Regulated nuclear transport is critical for the maintenance of the levels and activities of transcription factors, nuclear kinases, and replication factors. We identified Ca+2/calmodulin as an activator of nuclear import and suggested a role for Ca+2 in the regulation of nuclear import during cell activation. This evolutionarily ancient, calcium-dependent import pathway was proposed to facilitate uptake of a distinct subset of nuclear proteins during cell activation. The physiological significance of the Ca+2-calmodulin-regulated transport pathway became clear with the finding that defects in calmodulin-dependent nuclear import underlie certain forms of human sex reversal. The HMG-box architectural transcription factors SRY and SOX9 must enter the nucleus of Sertoli cells and bind tightly to target DNA for proper male gonad development. Thus, SRY acts as the primary trigger for maleness;nuclear transport of SRY is required to release this trigger. In a subset of human patients with autosomal sex reversal (Swyers syndrome, Campomelic dysplasia) nuclear transport of SRY and SOX9 is blocked. The mutations associated with these defects reside in a conserved calmodulin-binding motif near the amino terminus of SRY and SOX9. Thus, the SOX family of transcription factors appears to use Ca+2/calmodulin both as import receptor and molecular switch allowing for nuclear import and DNA binding. A similar autosomal sex reversal phenotype occurs when three insulin-related receptors are ablated in mice suggesting that intracellular signaling cascades may impact the normal functions of SRY and SOX9. More recently, the gene encoding TCF7L2 was shown to be a diabetes susceptibility locus in the Icelandic population. This transcription factor is a member of the HMG-box family containing a calmodulin-binding motif. The import of nuclear proteins by calmodulin, while functionally redundant with the canonic Ran-dependent pathway, is subject to independent regulation by intracellular Ca+2 mobilization. Abnormalities in calmodulin-dependent import emerge as the primary defect in patients with autosomal sex-reversal. These sex-reversal syndromes represent the first direct examples of a defect in a nuclear import pathway leading to human disease. Other human disorders involving SOX-family transcription factors may have similar defects in calmodulin dependent nuclear import. In addition to analysis of the import of the HMG-box transcription factors in mammals, we have recently shown that the calmodulin-dependent nuclear import pathway functions in yeast. We are currently taking genetic approaches to define additional components of this novel import pathway and seek to identify small molecule inhibitors of the process. Because the SOX2 protein is particularly important for Stem Cell pluripotency, our focus is currently on understanding the role of nuclear import in its regulation.

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Eustice, Moriah; Bond, Michelle R; Hanover, John A (2017) O-GlcNAc cycling and the regulation of nucleocytoplasmic dynamics. Biochem Soc Trans 45:427-436
Bulger, David A; Fukushige, Tetsunari; Yun, Sijung et al. (2017) Caenorhabditis elegans DAF-2 as a Model for Human Insulin Receptoropathies. G3 (Bethesda) 7:257-268
Fukushige, Tetsunari; Smith, Harold E; Miwa, Johji et al. (2017) A Genetic Analysis of the Caenorhabditis elegans Detoxification Response. Genetics 206:939-952
Olivier-Van Stichelen, St├ęphanie; Hanover, John A (2015) You are what you eat: O-linked N-acetylglucosamine in disease, development and epigenetics. Curr Opin Clin Nutr Metab Care 18:339-45
Bond, Michelle R; Hanover, John A (2015) A little sugar goes a long way: the cell biology of O-GlcNAc. J Cell Biol 208:869-80
Keembiyehetty, Chithra; Love, Dona C; Harwood, Katryn R et al. (2015) Conditional knock-out reveals a requirement for O-linked N-Acetylglucosaminase (O-GlcNAcase) in metabolic homeostasis. J Biol Chem 290:7097-113
Lewis, Brian A; Hanover, John A (2014) O-GlcNAc and the epigenetic regulation of gene expression. J Biol Chem 289:34440-8
Ghosh, Salil K; Bond, Michelle R; Love, Dona C et al. (2014) Disruption of O-GlcNAc Cycling in C. elegans Perturbs Nucleotide Sugar Pools and Complex Glycans. Front Endocrinol (Lausanne) 5:197
Abramowitz, Lara K; Olivier-Van Stichelen, St├ęphanie; Hanover, John A (2014) Chromosome imbalance as a driver of sex disparity in disease. J Genomics 2:77-88
Vigetti, Davide; Deleonibus, Sara; Moretto, Paola et al. (2014) Natural antisense transcript for hyaluronan synthase 2 (HAS2-AS1) induces transcription of HAS2 via protein O-GlcNAcylation. J Biol Chem 289:28816-26

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