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...n antiviral as well as antitumor capacity. The PML protein was recently shown to be covalently modified by the SUMO-1 protein (8, 60, 72). SUMO-1 is an 11.5kDa protein that is homologous to ubiquitin =-=(8, 39, 49, 54, 56, 70)-=-; however, SUMO-1 does not function in the same manner as ubiquitin. SUMO-1 becomes covalently attached to a variety of proteins, including PML, RanGAP1, and IkB, and serves to localize and/or stabili...

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...cted from its molecular mass, and analysis by mass spectrometry revealed that this form comprised an adduct of RanGAP with a novel, 8-kDa, ubiquitin-related polypeptide that was named GMP1, or SUMO-1 =-=(149, 152)-=-. A growing number of other proteins have since been found to be SUMO modified, including Mdm2 and p53, and in several cases SUMOylation plays a regulatory role, inhibiting ubiquitination and protein ...

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... protein (Ohtsubo et al., 1987, 1989) that generates RanGTP in the nucleus, whereas free RanGTP is depleted from the cytoplasm by RanGAP1, which is excluded from the nucleoplasm (Hopper et al., 1990; =-=Matunis et al., 1996-=-; Mahajan et. al, 1997). Thus, low RanGTP levels in the cytoplasm allow importin-� to bind -�, and the high RanGTP concentration in the nuclear compartment dissociates the importin complex. The concen...

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...ould have a variety of conseexpressing HA-SUMO-1. Western blot analysis withquences including changes in cellular localization (Maanti-Sp3 antibody revealed at least one additionalhajan et al., 1997; =-=Matunis et al., 1996-=-; Muller et al., slower migrating form of Sp3 in protein extracts from1998; Seeler et al., 2001). cells expressing HA-SUMO-1 (Figure 1A). To confirmSeveral transcription factors have recently been fou...

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...at, while sharing only 18% identity with Ub, also appear to be processed and covalently ligated to protein substrates by mechanisms similar to ubiquitination (Boddy et al., 1996; Mannen et al., 1996; =-=Matunis et al., 1996-=-; Okura et al., 1996; Shen et al., 1996a; Mahajan et al., 1997). The first member of this family of proteins, SUMO-1 (previously called GMP1, PIC1, UBL1, and Sentrin), was identified as a covalent mod...

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... 67), and chromosome segregation (68) have also been observed. Finally, ubiquitin-like proteins are involved in transcription (69), DNA repair (70), spindle-pole body duplication (71), nuclear import =-=(72, 73)-=-, and mitosis (74). Clearly, these processes are candidates for regulation by deubiquitinating enzymes. Crude preparations of enzymes capable of removing the ubiquitin from ubiquitinated histone H2a h...

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...lso known as sentrin or Ubl1 (Okura et al., 1996; Shen et al., 1996), or in yeast as Smt3 1 (Johnson et al., 1997), was originally discovered attached to the Ran GTPase-activating protein, RanGAP1 2 (=-=Matunis et al., 1996-=-; Mahajan et al., 1997), and has subsequently been shown to be conjugated to a rapidly growing set of substrates including I�B�, the inflammatory response regulatory protein (Desterro et al., 1998), a...

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...a role in the translocation itself is unknown. A major fraction of RanGAP is bound to the cytoplasmically oriented nucleoporin RanBP2 due to its modification by the ubiquitin-related modifier SUMO-1 (=-=Matunis et al., 1996-=-; Mahajan et al., 1997), and the remainder of RanGAP is soluble in the cytoplasm. RanBP2 has four RanGTP-binding domains (RBDs), which are similar in sequence to the RBD of the cytosolic protein RanBP...

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... (16). This effect of SUMO on biomolecular interactions also varies for different substrates. For example, sumoylation allows RanGAP1 to bind tightly to the nuclear pore complex protein RanBP2/Nup358 =-=(51,52)-=-, whereas SUMO-modified thymineDNA glycosylase showed a reduced affinity for the DNA substrate (53). Wakasugi and Sancar found that XPChHR23B participates in the initial assembly of the excision nucle...