A New Role for Wilms Tumor Protein 1: Differential Activities of plus KTS and -KTS Variants to Regulate LH beta Transcription

作者：Bagchi Debalina; Andrade Josefa; Shupnik Margaret A^*

来源：PLos One, 2015, 10(1): e0116825.

DOI：10.1371/journal.pone.0116825

Luteinizing hormone (LH) is synthesized and secreted throughout the reproductive cycle from gonadotrope cells in the anterior pituitary, and is required for steroidogenesis and ovulation. LH contains an a-subunit common with FSH, and a unique LH beta subunit that defines biological activity. Basal LH beta transcription is low and stimulated by hypothalamic GnRH, which induces synthesis of early growth response protein-1 (Egr1), and stimulates binding of transcription factors Egr1 and steroidogenic factor-1 (SF1) on the promoter. WT1 (Wilms tumor protein1) is a zinc finger transcription factor with an essential role in urogenital system development, and which regulates several reproductive genes via interactions with SF1 or binding to GC-rich elements such as Egr1 binding sites. We investigated a potential role for WT1 in LH beta transcription in clonal mouse gonadotrope L beta T2 cells. WT1 was present in L beta T2 and mouse pituitary cells, and protein bound to the endogenous LH beta promoter. Interestingly, mRNAs for WT1(+KTS), which contains a three amino-acid insertion between the 3rd and 4th zinc fingers, and the WT1 (-KTS) variant were both expressed at significant levels. WT1 mRNAs and protein were decreased approximately 50% by GnRH treatment, under conditions where Egr1 mRNA and protein, and LH beta transcription, were stimulated. Decreasing expression of mRNA for WT1 (-KTS) decreased stimulation of LH beta and Egr1 by GnRH, whereas decreasing both WT1 (-KTS) and (+KTS) increased endogenous LH beta transcription, and prevented LH beta but not Egr1 stimulation by GnRH, suggesting differing biological activities for the WT1 isoforms. Overexpression of WT1 showed that WT1(-KTS) enhanced LH beta promoter GnRH stimulation 2-to-3-fold and required the 3' Egr1 site, but WT1(+KTS) repressed both basal and GnRH-stimulated LH beta promoter activity by approximately 70%. Our data suggest that WT1 can modulate LH beta transcription, with differential roles for the two WT1 variants; WT1 (-KTS) enhances and WT1 (+KTS) suppresses transcription.

• 出版日期2015-1-24