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大部分真核生物mRNA的加工涉及到mRNA前体的分裂/多聚腺苷化,在3′-末端形成多聚腺苷酸(poly(A))尾巴.为了研究水稻mRNA前体多聚腺苷化过程所必需的poly(A)加尾信号、下游调控元件和poly(A)位点等序列的特点,用3′-末端带有poly(A)的EST与全长cDNA序列进行比较,建立了一个来自9953个基因的、覆盖12969条poly(A)位点两侧各40碱基序列的数据库.结果发现,只有7.9%的mRNA使用AAUAAA作为加尾信号,超过60%使用AAUAAA的1~2个碱基变化的序列作为加尾信号,11.5%的mRNA使用AAUGAA及其单碱基变化的加尾信号.在约25%的mRNA的3′-末端存在多个poly(A)位点.在90%的mRNA前体的加尾信号下游都能检测到富含U/GU的调控元件,尤其在以AAUAAA的多碱基变化序列作为加尾信号的mRNA前体中,半数以上都能在poly(A)位点两侧检测到下游调控元件.而且,这些调控元件的位置对poly(A)位点的选择有限制作用.总之,虽然水稻mRNA加尾信号的保守性较低,但大量下游调控元件的存在保证了多聚腺苷化过程的正常进行.
Processing of most eukaryotic mRNAs involves cleavage / polyadenylation of mRNA precursors to form polyadenylation (poly (A)) tail at the 3’-end To investigate the role of rice mRNA precursor polyadenylation The poly (A) -tagged ESTs at the 3’-end were compared with the full-length cDNA sequence for the poly (A) tailed signals, downstream regulatory elements and poly (A) A database of 9953 genes covering 40 base pairs of 12,969 poly (A) sites was constructed and found that only 7.9% of the mRNAs used AAUAAA as the tailed signal and over 60% of the AAUAAA-1 ~ 2 base-varied sequences as the tailed signal, 11.5% of the mRNA using AAUGAA and its single-base modified tail signal There are multiple poly (A) sites at the 3’-end of about 25% . U / GU-rich regulatory elements can be detected downstream of the tailed signal of 90% of mRNA precursors, especially in more than half of mRNA precursors that use the multi-base change sequence of AAUAAA as a tailed signal Downstream regulatory elements are detected on both sides of the poly (A) site.Moreover, the location of these regulatory elements has a limiting effect on the selection of the poly (A) site.In summary, although water Less conserved mRNA polyadenylation signal, but there are a large number of downstream regulatory elements ensuring normal polyadenylation process.