Methods and Compositions for Selecting siRNA of Improved Functionality

Abstract

Efficient sequence specific gene silencing is possible through the use of siRNA technology. Be selecting particular siRNAs by rational design, one can maximize the generation of an effective gene silencing reagent, as well as methods for silencing genes. Methods compositions, and kits generated through rational design of siRNAs are disclosed, including those directed to the nucleotide sequences for F12.

1 .- 15 . (canceled) 
     
     
         16 . An siRNA molecule comprising a duplex region of 18 to 30 base pairs in length, wherein
 the siRNA molecule targets a F12 (Factor XII) gene; and   the duplex region is of two separate strands of a sense strand and an antisense strand; and   the siRNA molecule comprises at least one of the following:   (1) a low GC content, preferably between about 30-52%,   (2) at least 2, preferably at least 3 A or U bases at positions 15-19 on the sense strand,   (3) an A base at position 19 of the sense strand,   (4) an A base at position 3 of the sense strand,   (5) a U base at position 10 of the sense strand,   (6) an A base at position 14 of the sense strand,   (7) a base other than C at position 19 of the sense strand,   (8) a base other than G at position 13 of the sense strand,   (9) a Tm that is preferably not stable at greater than 50° C.   (10) a base other than U at position 5 of the sense strand, and   (11) a base other than A at position 11 of the sense strand.   
     
     
         17 . The siRNA molecule of  claim 16 , where the 3′ end of the sense strand is position 19. 
     
     
         18 . The siRNA molecule of  claim 16 , wherein the siRNA molecule comprises a base other than C at position 19 of the sense strand, and a base other than G at position 13 of the sense strand. 
     
     
         19 . The siRNA molecule of  claim 16 , wherein the sense strand comprises a sequence homologous to one of SEQ ID NO:438-504, 506, 507, or 508. 
     
     
         20 . The siRNA molecule of  claim 16 , wherein the antisense strand and the sense strand are each 20 to 30 bases in length. 
     
     
         21 . The siRNA molecule of  claim 16 , wherein the siRNA molecule has at least one overhang region. 
     
     
         22 . A chemically synthesized double stranded siRNA molecule, wherein:
 (a) each strand of the double stranded siRNA molecule is between 18 and 30 bases in length; and   (b) one strand of the siRNA molecule comprises a sequence that is the complement of one of SEQ ID NO:438-504, 506, 507, or 508.   
     
     
         23 . The chemically synthesized double stranded siRNA molecule of  claim 22  wherein each strand of the siRNA molecule is 20-30 nucleotides in length. 
     
     
         24 . The siRNA molecule of  claim 16 , wherein the siRNA molecule comprises a 2′-position sugar modification. 
     
     
         25 . The siRNA molecule of  claim 24 , wherein the 2′-position sugar modification is selected from the group consisting of H, OR, R, halo, SH, SR, NH 2 , NHR, NR 2 , or CN, wherein R is an alkyl moiety. 
     
     
         26 . The siRNA molecule of  claim 16 , wherein the siRNA molecule comprises a non-natural phosphodiester linkage selected from a methylphosphonate, a phosphorothioate and a peptide.