Transcriptional activation of mouse TCR Jγ4 germline promoter by STAT5

The IL-7 receptor (IL-7R) controls the accessibility of mouse TCRγ locus, by recruiting STAT5 and transcriptional coactivators to the Jγ1 germline promoter and inducing histone acetylation at nearby chromatin. Although a STAT motif is present in Jγ4 germline promoter, it is still unknown whether STAT5 regulates the transcription of the Jγ4 promoter. Here, we showed that cytokine stimulation induced Jγ4-Cγ4 germline transcripts in a pre-T cell line, Scid.adh, and a hematopoietic cell line, Ba/F3. A STAT consensus motif was present in 5′ region of Jγ4 gene segment. We found that STAT5 bound to the STAT motif of the Jγ4 germline promoter in vitro by EMSA. In addition, we detected by chromatin immunoprecipitation assay that STAT5 was recruited to the endogenous Jγ4 chromatin in Ba/F3 cells after cytokine stimulation. Finally, using reporter assay, we showed that the Jγ4 germline promoter was activated by STAT5 and that mutation in the STAT motif abrogated the activity. Furthermore, this transactivation was augmented by transcriptional coactivators, CBP and p300. Collectively, these results demonstrate that STAT5 binds to the STAT motif in the Jγ4 promoter and induces germline transcription. Thus, this study indicates that the IL-7R/STAT5 signal controls the transcription and accessibility of different clusters in the TCRγ locus.