UNDERWRITING AGREEMENT

EXHIBIT 4.2

MORTGAGE ASSET SECURITIZATION TRANSACTIONS, INC.

March 24, 2006

New York, New York 10019

Mortgage Asset Securitization Transactions, Inc., a Delaware corporation (the “ Company ”), proposes to sell to UBS Securities LLC (the “ Underwriter ”), pursuant to this agreement (“ Agreement ”), the Company’s Mortgage Pass-Through Certificates, Series 2006-WMC1, Class A-1, Class A-2, Class A-3, Class A-4, Class M-1, Class M-2, Class M-3, Class M-4, Class M-5, Class M-6, Class M-7, Class M-8, Class-M-9 and Class M-10 Certificates (the “ Offered Certificates ” and, together with the Class CE, Class P, Class R and Class R-X Certificates, the “ Certificates ”) issued pursuant to the Pooling and Servicing Agreement, dated as of March 1, 2006 (the “ Pooling and Servicing Agreement ”), among the Company, as depositor, HomEq Servicing Corporation as servicer (the “ Servicer ”), Wells Fargo Bank, N.A, master servicer, trust administrator and custodian (the “ Master Servicer ”, the “Trust Administrator” and “Custodian”) and U.S. Bank National Association, as trustee (the “ Trustee ”). The Certificates will represent in the aggregate the entire beneficial ownership interest in a trust (the “ Trust ”) primarily consisting of a segregated pool (the “ Mortgage Pool ”) of one to four-family residential mortgage loans (the “ Mortgage Loans ”). Pursuant to the Assignment and Recognition Agreement, dated as of March 29, 2006 (the “ Assignment Agreement ”), among UBS Real Estate Securities Inc. (“ UBSRES ”), the Company and WMC Mortgage Corporation (“ WMC ”), the Mortgage Loans will be purchased from UBSRES by the Company in exchange for the Class CE and Class P Certificates and net proceeds from the sale of the remaining Certificates. The Offered Certificates are described more fully in Schedule A hereto and the Registration Statement (as hereinafter defined). This is to confirm the arrangements with respect to the Underwriter’s purchase of the Offered Certificates.

Reference is hereby made to (i) the Indemnification Agreement, dated as of March 24, 2006 (the “Trustee Indemnification Agreement”), between the Company and the Trustee; the Indemnification Agreement, dated as of March 24, 2006 (the “WMC Indemnification Agreement”), between the Company and WMC; the Indemnification Agreement, dated as of March 24, 2006 (the “HomEq Servicer Indemnification Agreement”), between the Company and the Servicer; the Indemnification Agreement, dated as of March 24, 2006 (the “Wells Fargo Master Servicer Indemnification Agreement”; collectively with the Trustee Indemnification Agreement, the WMC Indemnification Agreement and the HomEq Servicer Indemnification Agreement, the “Indemnification Agreements”), between the Company and the Master Servicer. The Pooling and Servicing Agreement, the Assignment Agreement and the Indemnification Agreements are collectively referred to herein as the “ Transaction Documents .” The Certificates are described more fully in the Prospectus (as hereinafter defined). Only the Offered Certificates are being sold pursuant to this Agreement.

The Company has filed with the Securities and Exchange Commission (the “ Commission ”) a registration statement on Form S-3 (No. 333-124678) for the registration of the Offered Certificates under the Securities Act of 1933 (the “ 1933 Act ”), which registration statement has become effective and copies of which, as amended to the date hereof, have been delivered to the Underwriter. The Company proposes to file with the Commission pursuant to Rule 424(b)(5) under the rules and regulations of the Commission under the 1933 Act, as amended (the “ 1933 Act Regulations ”) a prospectus supplement (the “ Prospectus Supplement ”), to the prospectus, dated June 2, 2005, included in such registration statement, relating to the Offered Certificates and the method of distribution thereof. Such registration statement on Form S-3, including exhibits thereto, as amended as of the date hereof, is hereinafter called the “ Registration Statement ”; and such prospectus, supplemented by the Prospectus Supplement or further supplement relating to the Offered Certificates, is hereinafter called the “ Prospectus .” The free writing prospectus, dated March 8, 2006 to the prospectus, dated June 2, 2005 which, is proposed to be used in connection with the sale of the Offered Certificates and filed with the Commission pursuant to Rule 433 under the 1933 Act, is hereinafter referred to as the “Preliminary Prospectus.”

SECTION 1.    Representations and Warranties . (i) The Company represents and warrants to the Underwriter as follows:

(a)    The Registration Statement, as amended as of the effective date thereof (the “ Effective Date ”), the Preliminary Prospectus, as of the date thereof and as of the date of the Contract of Sale, and the Prospectus, as of the date thereof, complied in all material respects with the requirements of the 1933 Act and the 1933 Act Regulations. The Registration Statement, as of the Effective Date, did not contain an untrue statement of a material fact or omit to state any material fact required to be stated therein or necessary to make the statements therein not misleading. The Preliminary Prospectus, as amended or supplemented as of its date and as of the date of the Contract of Sale and the Prospectus, as of the date thereof, did not, and as of the Closing Date will not, contain any untrue statement of a material fact or omit to state a material fact necessary in order to make the statements therein, in light of the circumstances under which they were made, not misleading; provided, however, that the representations and warranties in this subsection shall not apply to statements in or omissions from the Registration Statement, Preliminary Prospectus or Prospectus (A) arising from or included in the Company Information (as defined in the Indemnification Agreement) or (B) made in reliance upon and in conformity with information furnished to the Company in writing by the Underwriter expressly for use in the Registration Statement or Prospectus. The Company and the Underwriter hereby acknowledge that only the statements set forth on Exhibit A hereto (the “ Underwriter’s Information ”) constitute statements made in reliance upon and in conformity with information furnished to the Company in writing by the Underwriter expressly for use in the Registration Statement or Prospectus.

(b)    Since the respective dates as of which information is given in the Registration Statement, Preliminary Prospectus and Prospectus, except as otherwise stated therein, (A) there has been no material adverse change in the condition, financial or otherwise, or in the earnings, business affairs or business prospects of the Company, whether or not arising in the ordinary course of business, and (B) there have been no transactions entered into by the Company, other than those in the ordinary course of business, which are material with respect to the Company.

(c)    The Company has been duly incorporated and is validly existing as a corporation in good standing under the laws of the State of Delaware with corporate power and authority to own, lease and operate its properties and to conduct its business, as now conducted by it, and to enter into and perform its obligations under the Transaction Documents to which it is a party; and the Company is duly qualified as a foreign corporation to transact business and is in good standing in each jurisdiction in which such qualification is required, whether by reason of the ownership or leasing of property or the conduct of business.

(d)    The Company is not in violation of its charter or in default in the performance or observance of any material obligation, agreement, covenant or condition contained in any contract, indenture, mortgage, loan agreement, note, lease or other instrument to which the Company is a party, or to which any of the property or assets of the Company may be subject, or by which it or any of them may be bound; and the issuance and sale of the Offered Certificates to the Underwriter, the execution, delivery and performance of the Transaction Documents to which it is a party and the consummation of the transactions contemplated therein and herein and compliance by the Company with its obligations thereunder and hereunder have been duly authorized by all necessary corporate action and will not conflict with or constitute a breach of, or default under, or result in the creation or imposition of any lien, charge or encumbrance upon any property or assets of the Company pursuant to any material contract, indenture, mortgage, loan agreement, note, lease or other instrument to which the Company is a party or by which it or any of them may be bound, or to which any of the property or assets of the Company is subject, nor will such action result in any violation of the provisions of the charter or by-laws of the Company or any applicable law, administrative regulation or administrative or court decree.

(e)    There is no action, suit or proceeding before or by any court or governmental agency or body, domestic or foreign, now pending, or, to the knowledge of the Company, threatened, against or affecting the Company, which is required to be disclosed in the Registration Statement (other than as disclosed therein), or which might result in any material adverse change in the condition, financial or otherwise, or in the earnings, business affairs or business prospects of the Company, or which might materially and adversely affect the properties or assets thereof or which might materially and adversely affect the consummation of the transactions contemplated by the Transaction Documents to which it is a party; all pending legal or governmental proceedings to which the Company is a party or of which its property or assets is the subject which are not described in the Registration Statement, including ordinary routine litigation incidental to the business, are, considered in the aggregate, not material; and there are no contracts or documents of the Company which are required to be filed as exhibits to the Registration Statement by the 1933 Act or by the 1933 Act Regulations which have not been so filed.

(f)    No authorization, approval or consent of any court or governmental authority or agency is necessary in connection with the offering, issuance or sale of the Offered Certificates hereunder, except such as have been, or as of the Closing Date will have been, obtained or such as may otherwise be required under applicable state securities laws in connection with the purchase and offer and sale of the Offered Certificates by the Underwriter and any recordation of the respective assignments of the Mortgage Loans to the Trustee pursuant to the Pooling and Servicing Agreement that have not yet been completed.

(g)    The Company possesses all material licenses, certificates, authorities or permits issued by the appropriate state, federal or foreign regulatory agencies or bodies necessary to conduct the business now operated by it, and the Company has not received any notice of proceedings relating to the revocation or modification of any such license, certificate, authority or permit which, singly or in the aggregate, if the subject of an unfavorable decision, ruling or finding, would materially and adversely affect the condition, financial or otherwise, or the earnings, business affairs or business prospects of the Company.

(h)    Each of the Transaction Documents to which it is a party has been duly authorized, executed and delivered by the Company and constitutes a legal, valid and binding agreement enforceable against the Company in accordance with its terms, except as enforceability may be limited by (A) bankruptcy, insolvency, reorganization, receivership, moratorium or other similar laws affecting the enforcement of the rights of creditors generally, (B) general principles of equity, whether enforcement is sought in a proceeding in equity or at law, and (C) public policy considerations underlying the securities laws, to the extent that such public policy considerations limit the enforceability of the provisions of such Transaction Documents that purport to provide indemnification from securities law liabilities.

(i)    At the time of the execution and delivery of the Pooling and Servicing Agreement, the Company (i) will have good and marketable title to the Mortgage Loans being transferred by it to the Trustee pursuant thereto, free and clear of any lien, mortgage, pledge, charge, encumbrance, adverse claim or other security interest (collectively “ Liens ”), (ii) will not have assigned to any person any of its right, title or interest in such Mortgage Loans or in the Assignment Agreement or the Offered Certificates being issued pursuant to the Pooling and Servicing Agreement, and (iii) will have the power and authority to transfer such Mortgage Loans to the Trustee and sell the Offered Certificates to the Underwriter, and upon execution and delivery of the Pooling and Servicing Agreement, the Trustee will have acquired ownership of all of the Company’s right, title and interest in and to the related Mortgage Loans, and upon delivery to the Underwriter of the Offered Certificates, the Underwriter will have good and marketable title to the Offered Certificates, in each case free of Liens.

(j)    The Offered Certificates and the Pooling and Servicing Agreement will each conform in all material respects to the descriptions thereof contained in the Preliminary Prospectus and Prospectus, and the Offered Certificates, when duly and validly authorized, executed, authenticated and delivered in accordance with the Pooling and Servicing Agreement and paid for by the Underwriter as provided herein, will be entitled to the benefits of the Pooling and Servicing Agreement.

(k)    The Trust created by the Pooling and Servicing Agreement will not be required to be registered as an investment company under the Investment Company Act of 1940, as amended (the “ 1940 Act ”), and the Pooling and Servicing Agreement is not required to be qualified under the Trust Indenture Act of 1939, as amended (the “ Trust Indenture Act ”).

(l)    At the Closing Date, the Class A-1, Class A-2, Class A-3 and Class A-4 Certificates will be rated not lower than “Aaa” by Moody’s Investors Service, Inc. (“ Moody’s ”) and “AAA” by Standard & Poor’s, a division of The McGraw Hill Companies, Inc. (“ S&P ”). The Class M-1 Certificates will be rated not lower than “AA+” by S&P and “Aa1” by Moody’s, the Class M-2 Certificates will be rated not lower than “AA+” by S&P and “Aa2” Moody’s, the Class M-3 Certificates will be rated not lower than “AA” by S&P and “Aa3” by Moody’s, the Class M-4 Certificates will be rated not lower than “AA” by S&P and “A1” by Moody’s, the Class M-5 Certificates will be rated not lower than “AA-” by S&P and “A2” by Moody’s, the Class M-6 Certificates will be rated not lower than “A+” by S&P and “A3” by Moody’s, the Class M-7 Certificates will be rated not lower than “A” by S&P and “Baa1” by Moody’s, the Class M-8 Certificates will be rated not lower than “BBB+” by S&P and “Baa2” by Moody’s, the Class M-9 Certificates will be rated not lower than “BBB” by S&P and “Baa3” by Moody’s, and the Class M-10 Certificates will be rated not lower than “BBB-” by S&P and “Ba1” by Moody’s.

(m)    Any taxes, fees and other governmental charges in connection with the execution, delivery and issuance of the Transaction Documents to which it is a party and the Offered Certificates have been paid or will be paid at or prior to the Closing Date.

(n)    The sale of the Mortgage Loans to the Trustee on the Closing Date and the sale by the Company of the Offered Certificates will be treated by the Company for financial accounting and reporting purposes as a sale of assets and not as a pledge of assets to secure debt

(o)    As of the Effective Date and as of the date of the Contract of Sale, the Depositor is not and will not be as of the Closing Date an “ineligible issuer” as defined in Rule 405 of the Securities Act.

(p)    Any certificate signed by any officer of the Company and delivered to the Underwriter or its counsel shall be deemed a representation and warranty by the Company to the Underwriter as to the matters covered thereby.

(q)    As of the Contract of Sale, the Preliminary Prospectus did not include any untrue statement of a material fact or omission of any material fact necessary in order to make the statements therein, in light of the circumstances under which they were made, not misleading.

(r)    No Advisory or Fiduciary Responsibility.

The Company acknowledges and agrees that: (i) the purchase and sale of the Offered Certificates pursuant to this Agreement, including the determination of the offering price of the Offered Certificates and any related discounts and commissions, is an arm’s-length commercial transaction between the Company and the Underwriter and the Company is capable of evaluating and understanding and understands and accepts the terms, risks and conditions of the transactions contemplated by this Agreement; (ii) in connection with each transaction contemplated hereby and the process leading to such transaction each Underwriter is and has been acting solely as a principal and is not the agent or fiduciary of the Company, or its respective affiliates, stockholders, creditors or employees or any other party; (iii) the Underwriter has not assumed or will assume an advisory or fiduciary responsibility in favor of the Company with respect to any of the transactions contemplated hereby or the process leading thereto (irrespective of whether such Underwriter has advised or is currently advising the Company on other matters) or any other obligation to the Company except the obligations expressly set forth in this Agreement; (iv) the Underwriter and its affiliates may be engaged in a broad range of transactions that involve interests that differ from those of the Company and that the Underwriter has no obligation to disclose any of such interests by virtue of any fiduciary or advisory relationship; and (v) the Underwriter has not provided any legal, accounting, regulatory or tax advice with respect to the offering contemplated hereby and the Company has consulted its own legal, accounting, regulatory and tax advisors to the extent it deemed appropriate.

This Agreement supersedes all prior agreements and understandings (whether written or oral) between the Company and the Underwriter, or any of them, with respect to the subject matter hereof. The Company hereby waives and releases, to the fullest extent permitted by law, any claims that the Company may have against the Underwriter with respect to any breach or alleged breach of fiduciary duty.

SECTION 2.    Purchase and Sale . Subject to the terms and conditions herein set forth and in reliance upon the representations and warranties herein contained, the Company agrees to sell to the Underwriter, and the Underwriter agrees to purchase from the Company, at a purchase price set forth on Schedule A hereto, the principal amount of the Offered Certificates set forth on Schedule A hereto.

SECTION 3.    Delivery and Payment . Payment of the purchase price for, and delivery of, the Offered Certificates to be purchased by the Underwriter shall be made at the office of Thacher Proffitt & Wood llp, Two World Financial Center, New York, New York 10281, or at such other place as shall be agreed upon by the Underwriter and the Company, at 10:00 A.M. New York City time, on March 29, 2006, which date and time may be postponed by agreement between you and the Company (such time and date of payment and delivery being herein called the “ Closing Date ”). Payment shall be made to the Company, at its option, by (i) appropriate notation of an inter company transfer between affiliates of UBS Securities LLC or (ii) in immediately available Federal funds wired to such bank as may be designated by the Company, against delivery of the Offered Certificates. The Offered Certificates shall be in such denominations and registered in such names as the Underwriter may request in writing at least two business days before Closing Date. The Offered Certificates will be made available for examination and packaging by the Underwriter not later than 10:00 A.M. on the last business day prior to Closing Date.

SECTION 4.    Covenants of the Company .

(i)    The Company covenants with the Underwriter as follows:

(a)    The Company will give the Underwriter notice of its intention to file or prepare any amendment to the Registration Statement, any amendment or supplement to the Preliminary Prospectus, Prospectus Supplement, or any amendment or supplement to the Prospectus (including any revised prospectus which the Company proposes for use by the Underwriter in connection with the offering of the Offered Certificates which differs from the prospectus on file at the Commission at the time the Registration Statement becomes effective, whether or not such revised prospectus is required to be filed pursuant to Rule 433 or Rule 424(b) of the 1933 Act Regulations), will furnish the Underwriter with copies of any such amendment or supplement a reasonable amount of time prior to such proposed filing or use, as the case may be, and will not file any such amendment or supplement or use any such prospectus to which the Underwriter shall reasonably object.

(b)    The Company will cause the Preliminary Prospectus to be transmitted to the Commission for filing pursuant to Rule 433 under the 1933 Act by means reasonably calculated to result in filing with the Commission pursuant to said rule. The Company will cause the Prospectus Supplement and Prospectus to be transmitted to the Commission for filing pursuant to Rule 424(b)(5) under the 1933 Act by means reasonably calculated to result in filing with the Commission pursuant to said rule.

(c)    The Company will deliver to the Underwriter as many signed copies of the Registration Statement as originally filed and of each amendment thereto (including exhibits filed therewith or incorporated by reference therein) as the Underwriter may reasonably request and will also deliver to the Underwriter a conformed copy of the Registration Statement as originally filed and of each amendment thereto (without exhibits).

(d)    The Company will furnish to the Underwriter, from time to time during the period when the Preliminary Prospectus or Prospectus is required to be delivered under the 1933 Act or the Securities Exchange Act of 1934, as amended (the “ 1934 Act ”), such number of copies of the Preliminary Prospectus or Prospectus (as amended or supplemented) as the Underwriter may reasonably request for the purposes contemplated by the 1933 Act or the 1934 Act or the respective applicable rules and regulations of the Commission thereunder.

(e)    If during the period after the first date of the public offering of the Offered Certificates in which a prospectus relating to the Offered Certificates is required to be delivered under the 1933 Act, any event shall occur as a result of which it is necessary, in the opinion of counsel for the Underwriter, to amend or supplement the Prospectus in order to make the Prospectus not misleading in the light of the circumstances existing at the time it is delivered to a purchaser, the Company will forthwith amend or supplement the Prospectus (in form and substance satisfactory to counsel for the Underwriter) so that, as so amended or supplemented, the Prospectus will not include an untrue statement of a material fact or omit to state a material fact necessary in order to make the statements therein, in the light of the circumstances existing at the time it is delivered to a purchaser, not misleading, and the Company will furnish to the Underwriter a reasonable number of copies of such amendment or supplement.

(f)    The Company will endeavor to arrange for the qualification of the Offered Certificates for sale under the applicable securities laws of such states and other jurisdictions of the United States as the Underwriter may designate; provided, however, that the Company shall not be obligated to qualify as a foreign corporation in any jurisdiction in which it is not so qualified. In each jurisdiction in which the Offered Certificates have been so qualified, the Company will file such statements and reports as may be required by the laws of such jurisdiction to continue such qualification in effect for a period of not less than one year from the effective date of the Registration Statement.

(g)    The Company will use the net proceeds received by it from the sale of the Offered Certificates in the manner specified in the Prospectus under “ Use of Proceeds .”

(h)    If the transactions contemplated by this Agreement are consummated, the Company will pay or cause to be paid all expenses incident to the performance of the obligations of the Company under this Agreement, and will reimburse the Underwriter for any reasonable expenses (including reasonable fees and disbursements of counsel) reasonably incurred by them in connection with qualification of the Offered Certificates for sale and determination of their eligibility for investment under the laws of such jurisdictions as the Underwriter has reasonably requested and the printing of memoranda relating thereto, for any fees charged by investment rating agencies for the rating of the Offered Certificates, and for expenses incurred in distributing the Preliminary Prospectus or Prospectus (including any amendments and supplements thereto) to the Underwriter. Except as herein provided, the Underwriter shall be responsible for paying all costs and expenses incurred by them, including the fees and disbursements of counsel, in connection with the purchase and sale of the Offered Certificates.

(i)    If, during the period after the Closing Date in which a prospectus relating to the Offered Certificates is required to be delivered under the 1933 Act, the Company receives notice that a stop order suspending the effectiveness of the Registration Statement or preventing the offer and sale of the Offered Certificates is in effect, the Company will immediately advise the Underwriter of the issuance of such stop order. The Company will m