ИСТИНА

Recent comparisons of human and mouse genomes revealed significant levels of sequence and organizational similarity. As part of a continuing effort to expand the Encyclopedia of DNA Elements (ENCODE), here we have extensively studied the transcriptomes of the two species by RNA-seq using a panel of diverse tissues and cell lines and extended the existing catalogues of orthologous transcriptional elements (long non-coding RNAs, pseudogenes, exons, and splice junctions) by specifically developed computational pipelines. Our data has uncovered many novel transcriptional elements contributing to the characterization of the human and mouse transcriptomes confirming previous observations according to which mammalian genomes are pervasively transcribed. We have found that many features associated with the average steady-state RNA production exhibit significant similarity between human and mouse. Namely, we have found that the average expression levels are highly correlated between orthologous 100~bp sequence windows and even between entire regions corresponding to orthologous protein-coding genes. This suggests that average expression levels of a substantial fraction of mammalian genes have been established prior to the split of human and mouse. Interestingly, the degree of similarity of transcriptional levels at orthologous loci is virtually independent from sequence conservation at proximal regulatory regions. Additionally, we report substantial similarity between expression profiles of orthologous long non-coding RNAs, and also between transcriptional levels in orthologous intergenic regions.