The transcription factor STAT5 is fundamental to the mammalian immune system. However, the relationship between its two paralogs, STAT5A and STAT5B, and the extent to which they are functionally distinct, remains controversial. We addressed this longstanding question in primary CD4+ 'helper' T cells, the principal orchestrators of adaptive immunity. Using a combination of genetic and genomic approaches, we demonstrate that, although both influence regulatory (Treg) and effector T cell responses, and control many of the same genes, they are not functionally equivalent and, in fact, only the latter is required for immunological tolerance. Differences in genomic distribution and transcriptomic output support the conclusion that STAT5B is dominant and, surprisingly, point towards relative abundance (i.e. paralog dose), rather than unique functional capabilities, as the principal distinguishing feature. Collectively, our data provide a unifying model for the discrete and redundant activities of STAT5A and STAT5B, establishing that asymmetrical expression underlies paralog specificity (or dominance) in the face of widespread structural homology. SOURCE: Yuka Kanno (kannoy@mail.nih.gov) - LCBS-MIIB NIH

Pluto Bioinformatics

GSE77656: STAT5 paralog dose governs T cell effector and regulatory function