Mortality Factor 4 (MORF4)

MORF4 induces a senescent-like phenotype in immortal cell lines assigned to complementation group B with concomitant changes in 2 markers of senescence. Overexpression of MORF4 in HeLa cells ultimately caused abnormal nuclear morphology and cell death.

The deduced 235-amino acid protein contains a bipartite nuclear localization signal, a helix-loop-helix domain, a region showing similarity to Drosophila Msl3, and a C-terminal leucine zipper motif. It also has a putative cAMP phosphorylation site, a protein kinase C phosphorylation site, and a tyrosine phosphorylation site. RT-PCR analysis showed MORF4 present at very low levels in multiple normal and immortal human cell lines. Transient transfection of HeLa cells with fluorescence-tagged MORF4 resulted in nuclear localization.