Next week, we'll hear from Sahin about his work: “Survival on amniote sex chromosomes is associated with a unique combination of transcription factor binding and microRNA-mediated repression." See you then!
Abstract: To date, analyses of amniote sex chromosome evolution have primarily focused on protein-coding sequence, with little known about the role of regulatory non-coding sequence. Previous studies identified two independent gene sets with ancestral homologs on the X(Z) chromosome that survived Y(W)-linked degeneration (X-Y pairs, Z-W pairs). Here, we reanalyze existing datasets on microRNA (miRNA) targeting and transcription factor (TF) binding to show that X-Y and Z-W pairs’ dosage is controlled by these two widely studied gene regulatory mechanisms. We provide evidence that X-Y and Z-W pairs are sensitive to over-expression and thus extensively targeted by miRNAs in order to tune expression levels. Genes that evolved to undergo X-inactivation are also likely sensitive to over-expression; they too show increased miRNA-mediated regulation. Furthermore, the promoter/enhancer regions of both X-Y pairs and the autosomal orthologs of Z-W pairs are highly bound by sequence-specific TFs. Thus, a combination of TF- and miRNA-mediated regulation likely maintains the expression of X-Y and Z-W pairs within narrow windows across tissues and cell-types.