The Class PO Securities are Principal Only Securities. Principal Only Securities are treated for federal income tax purposes as having been issued with an amount of original issue discount ("OID") equal to the difference between their principal balance and their issue price. The  Class  FI,  SI  and  QA  Securities  are  "Interest  Weighted  Securities"  as  described  in "Certain Federal Income Tax Consequences – Tax Treatment of Regular Securities – Interest Weighted Securities and Non-VRDI Securities" in the Base Offering Circular. Although the tax treatment  of  Interest  Weighted  Securities  is  not  entirely  certain,  Holders  of  the  Interest Weighted Securities should expect to accrue all income on these Securities (other than income attributable to market discount or de minimis market discount) under the OID rules based on the expected payments on these Securities at the prepayment assumption described below. The Class FZ, Z, and ZA Securities are Accrual Securities. Holders of Accrual Securities are required to accrue all income from their Securities (other than income attributable to market discount or de minimis market discount) under the OID rules based on the expected payments on the Accrual Securities at the prepayment assumption described below. In addition to the Regular Securities described in the preceding three paragraphs, based on anticipated prices (including accrued interest), the assumed Mortgage Loan characteristics, the prepayment assumption described below and, in the case of the Floating Rate Classes (other than Class FX), the constant LIBOR value described below, Class FX is expected to be issued with OID. Prospective investors in the Regular Securities should be aware, however, that the forego- ing  expectations  about  OID  could  change  because  of  differences  (1)  between  anticipated purchase prices and actual purchase prices or (2) between the assumed characteristics of the Trust Assets and the characteristics of the Trust Assets actually delivered to the Trust. The prepayment assumption that should be used in determining the rates of accrual of OID, if any, on the Regular Securities is 170% % PSA in the case of the Group 1 Securities  and 352% PSA in the case of the Group 2 Securities (as described in "Yield, Maturity and Prepayment Considera- tions" in this Supplement). In the case of the Floating Rate Classes, the constant value of LIBOR to be used for these determinations is 5.12%. No representation is made, however, about the rate at which prepayments on the Mortgage Loans underlying the any Group of Trust Assets actually will occur or the level of LIBOR at any time after the date of this Supplement. See "Certain Federal Income Tax Consequences" in the Base Offering Circular. The  Regular  Securities  generally  will  be  treated  as  "regular  interests"  in  a  REMIC  for domestic building and loan associations and "real estate assets" for real estate investment trusts ("REITs") as described in "Certain Federal Income Tax Consequences" in the Base Offering Circular. Similarly, interest on the Regular Securities will be considered "interest on obliga- tions secured by mortgages on real property" for REITs. Residual Securities The Class RR Securities will represent the beneficial ownership of the Residual Interest in the Pooling REMIC and the beneficial ownership of the Residual Interest in the Issuing REMIC. The Residual Securities, i.e., the Class RR Securities, generally will be treated as "residual interests" in a REMIC for domestic building and loan associations and as "real estate assets" for REITs,  as  described  in  "Certain  Federal  Income  Tax  Consequences"  in  the  Base  Offering Circular, but will not be treated as debt for federal income tax purposes. Instead, the Holders of the Residual Securities will be required to report, and will be taxed on, their pro rata shares of the taxable income or loss of the Trust REMICs, and these requirements will continue until there  are  no  Securities  of  any  Class  outstanding.  Thus,  Residual  Holders  will  have  taxable income attributable to the Residual Securities even though they will not receive principal or interest distributions with respect to the Residual Securities, which could result in a negative S-27