The Function Of ElciRNA And ASAT SiRNA

Part I:The RNAi machinery has been clarified as a mighty regulator in a huge number of life events, such as gene transcription. However, whether the RNAi machinery participates into the mitotic chromosome segregation in mammalian cells remains elusive until now. Here we report that Dicer and AGO2, two central components of the mammalian RNAi pathway participate into the chromosome segregation directly. Knockdown of Dicer or AG02 leads to a higher incidence of chromosome lagging phenotype, and this effect is independent from microRNAs pathway as examined with DGCR8 knockout cells. Further investigation in the molecular mechanism has demonstrated that a-satellite RNA, a well-known noncoding RNA derived from centromeric repeat region, is managed by AG02 under the guidance of endogenous small interference RNAs, and the slicer activity of AG02 is indispensible. Level and distribution of chromosome associated a-satellite RNA have crucial regulatory effect on the localization of centromeric proteins such as centromere protein C1 (CENPC1). With these results, we also provide a paradigm in which RNAi pathway participates into myriads of vital cellular events though the maintenance of level and distribution of noncoding RNAs in mammalian cells.Part II:Noncoding RNAs regulate gene expression through diverse mechanisms. Recently a large number of circular RNAs were identified in animal cells, and some of them were shown to function as microRNA sponges. We demonstrated that a subset of exon/intron circular RNAs (circRNAs) were associated with RNA polymerase II, and promoted gene transcription in cis. We showed that these circRNAs had localization in the nucleus, and analyzed genomic elements required for the circularization. Our results indicated that these circRNAs were functional sponge for splicing factors such as U1 RNA at least to promote the transcription initiation of their parent genes. Thus, these circRNAs kept local concentration of splicing factors high to facilitate gene expression, and DNA sequences generating these exon/intron circRNAs could be viewed as build-in elements enhancing the expression of their parent genes in animal cells.