AUTHOR=Xu Haidong , Ma Guangwei , Mu Fang , Ning Bolin , Li Hui , Wang Ning 

TITLE=STAT3 Partly Inhibits Cell Proliferation via Direct Negative Regulation of FST Gene Expression

JOURNAL=Frontiers in Genetics

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/genetics/articles/10.3389/fgene.2021.678667

DOI=10.3389/fgene.2021.678667

ISSN=1664-8021

ABSTRACT=<p>Follistatin (FST) is a secretory glycoprotein and belongs to the TGF-β superfamily. Previously, we found that two single nucleotide polymorphisms (SNPs) of sheep <italic>FST</italic> gene were significantly associated with wool quality traits in Chinese Merino sheep (Junken type), indicating that FST is involved in the regulation of hair follicle development and hair trait formation. The transcription regulation of human and mouse <italic>FST</italic> genes has been widely investigated, and many transcription factors have been identified to regulate <italic>FST</italic> gene. However, to date, the transcriptional regulation of sheep <italic>FST</italic> is largely unknown. In the present study, genome walking was used to close the genomic gap upstream of the sheep genomic <italic>FST</italic> gene and to obtain the <italic>FST</italic> gene promoter sequence. Transcription factor binding site analysis showed sheep <italic>FST</italic> promoter region contained a conserved putative binding site for signal transducer and activator of transcription 3 (STAT3), located at nucleotides −423 to −416 relative to the first nucleotide (A, +1) of the initiation codon (ATG) of sheep <italic>FST</italic> gene. The dual-luciferase reporter assay demonstrated that STAT3 inhibited the <italic>FST</italic> promoter activity and that the mutation of the putative STAT3 binding site attenuated the inhibitory effect of STAT3 on the <italic>FST</italic> promoter activity. Additionally, chromatin immunoprecipitation assay (ChIP) exhibited that STAT3 is directly bound to the <italic>FST</italic> promoter. Cell proliferation assay displayed that FST and STAT3 played opposite roles in cell proliferation. Overexpression of sheep <italic>FST</italic> significantly promoted the proliferation of sheep fetal fibroblasts (SFFs) and human keratinocyte (HaCaT) cells, and overexpression of sheep <italic>STAT3</italic> displayed opposite results, which was accompanied by a significantly reduced expression of <italic>FST</italic> gene (<italic>P</italic> &lt; 0.05). Taken together, STAT3 directly negatively regulates sheep <italic>FST</italic> gene and depresses cell proliferation. Our findings may contribute to understanding molecular mechanisms that underlie hair follicle development and morphogenesis.</p>