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Enhanced autophagic cell death in expanded polyhistidine variants of HOXA1 reduces PBX1‐coupled transcriptional activity and inhibits neuronal differentiation
Author(s) -
Paraguison Rubigilda C.,
Higaki Katsumi,
Yamamoto Kenji,
Matsumoto Hideo,
Sasaki Tsukasa,
Kato Nobumasa,
Nanba Eiji
Publication year - 2006
Publication title -
journal of neuroscience research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.72
H-Index - 160
eISSN - 1097-4547
pISSN - 0360-4012
DOI - 10.1002/jnr.21137
Subject(s) - biology , ectopic expression , programmed cell death , microbiology and biotechnology , homeobox , enhancer , neurite , retinoic acid , gene , genetics , gene expression , apoptosis , in vitro
HOXA1 is a member of the homeobox gene family and is involved in early brain development. In our previous study, we identified novel variants of polyhistidine repeat tract in HOXA1 gene and showed that ectopic expression of expanded variants led to enhanced intranuclear aggregation and accelerated cell death in a time‐dependent manner. Here, we further investigate the implications of polyhistidine variants on HOXA1 function. Aside from intranuclear aggregation, we observed cytosolic aggregates during the early stages of expression. Rapamycin, an autophagy inducer, resulted in decreased protein aggregation and cell death. Here, we also show an interaction between variants of HOXA1 and one of the HOX protein known cofactors, PBX1. Expanded HOXA1 variants exhibited reduced PBX1‐coupled transcriptional activity through a regulatory enhancer of HOXB1. Moreover, we demonstrate that both deleted and expanded variants inhibited neurite outgrowth in retinoic acid‐induced neuronal differentiation in neuroblastoma cells. These results provide further evidence that expanded polyhistidine repeats in HOXA1 enhance aggregation and cell death, resulting in impaired neuronal differentiation and cooperative binding with PBX1. © 2006 Wiley‐Liss, Inc.