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1: Nat Cell Biol. 2007 May;9(5):596-603. Epub 2007 Apr 15.
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N-terminal alpha-methylation of RCC1 is necessary for stable chromatin association and normal mitosis.

Chen T, Muratore TL, Schaner-Tooley CE, Shabanowitz J, Hunt DF, Macara IG.

Department of Microbiology, Center for Cell Signaling, University of Virginia School of Medicine University of Virginia, Charlottesville, VA 22908-0577, USA.

Regulator of chromatin condensation 1 (RCC1) is the only known guanine nucleotide-exchange factor for the Ran GTPase and has pivotal roles in nucleo-cytoplasmic transport, mitosis, and nuclear-envelope assembly. RCC1 associates dynamically with chromatin through binding to histones H2A and/or H2B in a Ran-regulated manner. Here, we report that, unexpectedly, the amino-terminal serine or proline residue of RCC1 is uniquely methylated on its alpha-amino group. Methylation requires removal of the initiating methionine, and the presence of proline and lysine at positions 3 and 4, respectively. Methylation-defective mutants of RCC1 bind less effectively than wild-type protein to chromatin during mitosis, which causes spindle-pole defects. We propose a bimodal attachment mechanism for RCC1 in which the tail promotes stable RCC1 association with chromatin through DNA binding in an alpha-N-methylation-dependent manner. These data provide the first known function for N-terminal protein methylation.

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PMID: 17435751 [PubMed - indexed for MEDLINE]