The Probable Relationship Between Human miRNA Genes and Transcription

[[abstract]]MicroRNAs ( miRNAs ) are about 22 nucleotides long small regulatory RNAs produced from hairpin-like precursors, and suppressing translation of target genes by binding to their mRNA. For this reason, miRNAs play the role of gene regulation in disease and health. Upstream regions of genes are associated with transcription, and it is known that they could have one or many transcript start sites in eukaryotes, and are named promoter regions. CpG islands are typically common near transcription start sites in vertebrates, often associated with promoter regions, and some of which are hypermethylated in cancer . First, we focused on identifying human miRNA genes that are located near CpG island regions or promoter regions as well. It is found that a subset of miRNA genes is CpG islands-associated, in which a highly significant proportion of miRNA genes ( 74 of 462, i.e. 16.0 % ) are located within 1000 bp of a CpG island. It is also found that 10 of 462 miRNA genes are located within promoter regions, 7 of 10 miRNA genes from promoter regions are associated with CpG islands. Second, we study the possible of mature miRNAs that could target promoter regions. It is found that some of the targeted sites could overlap TF-binding sites, showing mature miRNAs maybe affect transcription of coding genes. Third, we produced a new protocol of predicting pre-miRNA candidates from intron or intergenic regions. According to our study, we have confirmed that 5 of 6 pre-miRNA candidates are associated with CpG islands, but none of them are located within promoter regions. The 6 miRNA precursor (mature) candidates are highly similar to the pre-miRNA, hsa-mir-566, which have a sequence similarity ranged from 63 to 83 % ( 79 to 89 % ). In summary our study suggesting that these miRNAs maybe have a potential role in CpG islands methylation, involving in development and carcinogenesis. In vitro or in vivo experiments are required to perform in order to verify these candidates as new miRNA genes. Fourthermore, it is suspected that miRNA genes close to or overlapping with CpG islands and within promoter regions could be involved in autoregulation of methylation