HEY1 Leu94Met gene polymorphism dramatically modifies its biological functions

Abstract

The hairy/enhancer-of-split related with YRPW motif 1 (HEY1) is a member of the basic-helix-loop-helix-Orange (bHLH-O) family of transcriptional repressors that mediate Notch signaling. Several cancer-related pathways also regulate HEY1 expression, and HEY1 itself acts as an indirect positive regulator of the p53 tumor suppressor protein and a negative regulator of androgen receptor activity. In this study we show how a naturally occurring non-synonymous polymorphism at codon 94 of HEY1, which results in a substitution of leucine by methionine (Leu94Met), converts HEY1 from an androgen receptor corepressor to an androgen receptor co-activator without affecting its intrinsic transcriptional repressive domains. The polymorphism Leu94Met also abolishes HEY1-mediated activation of p53 and suppresses the ability of HEY1 to induce p53-dependent cell-cycle arrest and aberrant cell differentiation in human osteosarcoma U2OS cells. Moreover, expression of HEY1, but not of the variant Leu94Met, confers sensitivity to p53-activating chemotherapeutic drugs on U2OS cells. In addition, we have identified motifs in HEY1 that are critical for the regulation of its subcellular localization and analysed how mutations in those motifs affect both HEY1 and HEY1-Leu94Met functions. These findings suggest that the polymorphism Leu94Met in HEY1 radically alters its biological activities and may affect oncogenic processes.

The transcription factor CREBZF is a novel positive regulator of p53

“…9 In addition to these genetic studies, an expression analysis found that the majority of prostate samples showed total exclusion of HEY1 protein from the nucleus, 10 an abnormality that prevents HEY1-dependent p53 activation. 3 Thus, alterations in HEY1 function and/or expression could contribute to the oncogenic transformation, impairing the crosstalk between Notch and p53 or other signaling pathways.…”

“…1 Hairy/enhancer-of-split related with YRPW motif 1 (HEY1), a well-characterized effector within the Notch signaling, has been recently identified as a new p53 co-regulator. 2,3 Initially, a genome-wide functional analysis revealed that HEY1 is a positive regulator of p53 through repression of MDM2 transcription, although the detailed molecular mechanisms responsible for this regulation are still unknown. 2 Subsequently, our laboratory showed that HEY1 expression impairs cell proliferation in human osteosarcoma cells (U2OS) in a p53-dependent manner and sensitizes cells to p53-activating chemotherapeutic drugs.…”

Hey Factors at the Crossroad of Tumorigenesis and Clinical Therapeutic Modulation of Hey for Anticancer Treatment

“…For instance, nonsynonymous single-nucleotide polymorphism (SNP) naturally occurs at codon 94 of Hey1, which leads to a substitution of a leucine residue by methionine (L94M) in the helix 2 domain. The L94M-mutant Hey1 transforms from an androgen receptor corepressor to androgen receptor coactivator without changing its intrinsic repressive domains (14). The phosphorylation of the Serine-68 residue of Hey1 prevents its enhancement of p53 transcriptional activation but confers p53-activating chemotherapy resistance, whereas wild-type Hey1 stimulates p53 and alters the sensitivity to p53-activating chemotherapy drugs.…”

“…It should be noted that the specificity for protein interactions and target molecules of different Hey variants is differential between certain cell types. L94M Hey1 variant strongly interacts with Hey2, whereas Hey1 forms an unstable homodimer with Hey2 (14). There is a potential, unknown Hey1 variant enhancing matrix metallopeptidase 9 (MMP9) expression in osteosarcoma, whereas wild-type Hey1 is unable to bind to the MMP9 promoter itself (16).…”

“…The upregulation of Hey1 is likely to inhibit differentiation because rhabdomyosarcoma cells with an shRNA antagonizing Hey1 display differentiation morphology changes and the expression of differentiation marker myogenin (22). The introduction of Hey1 into proliferating osteosarcoma increases p53 expression and makes tumor cells stay in a nondividing state through p53-dependent reversible cell-cycle arrest (14). In the context of quiescence, elevated Hey family expression can reflect the undifferentiating property of malignant cancer cells.…”