![]() ![]() Has been controversial, current evidence suggests that the nucleus is indeed highly ordered with a high degree of structuralįlexibility ( Lamond and Earnshaw 1998). Although the biological significance of the nuclear scaffold Repeat region for coiled-coil formation flanked by globular domains. Indeed, SMC proteins superficially resemble intermediate filaments inasmuch as they contain an internal α-helical heptad Most abundant component (after topoisomerase II) of the mitotic nuclear scaffold or matrix ( Saitoh et al. SMC proteins also function as chromosome structural components-the chicken SMC protein ScII, for example, being the second Other biochemical and genetic interactions between SMC proteins and non-SMC proteins have also been reported ( Hirano 1999). To changes in chromosome structure ( Hirano 1999). SMC complexes may act as DNA crosslinkers with the flexible hinge facilitating an ATP-modulated scissorslike motion linked In Xenopus laevis, for example, the SMC heterodimer XCAP-E/XCAP-C interacts with the non-SMC subunits XCAP-G, XCAP-D2, and XCAP-H to form aĬondensin complex that converts interphase chromatin into mitoticlike chromosomes ( Hirano et al. In eukaryotes, SMC dimers interact with non-SMC subunits to form condensin andĬohesin complexes. SMC2/SMC4ĭimers are involved in chromosome condensation and dosage compensation, whereas SMC1/SMC3 dimers are involved in sister chromatidĬohesion and DNA recombination and repair. There are four classes of SMC proteins (SMC1–SMC4) that form two types of heterodimers: SMC1/SMC3 and SMC2/SMC4. Two SMC subunits has been proposed to produce a functional dimer with ATP-binding sites at each end ( Melby et al. An antiparallel coiled-coil interaction between Α-helical coiled coils between which is inserted a putative flexible hinge. 1994), but are unique inasmuch as their Walker A and B ATP-binding sites are separated by two sizable regions predicted to form SMC proteins are ATPases evolutionarily related to ABC transporters ( Saitoh et al. Is important for compacting DNA into the tight confines of the nucleus ( Hirano 1999). Structural maintenance of chromosome (SMC) proteins appear to play a dynamic role in packaging and shaping chromosomes, which Proteins and suggests that HEAT repeats may play important roles in chromosome dynamics. Hence, our analysis predicts structural features of these HEAT repeats also were found in dis1-TOGįamily and cofactor D family microtubule-associated proteins, which, owing to their roles in microtubule dynamics, performįunctions related to mitotic progression and chromosome segregation. SWI2/SNF2 proteins, some of which are helicases, perform diverse roles in transcriptionĬontrol, DNA repair, and chromosome segregation and form chromatin-remodeling complexes. Which is a member of the SWI2/SNF2 family. Were also found in the TBP-associated TIP120 protein, a global enhancer of transcription, and in the budding yeast Mot1p protein, Clathrin adaptor and COP-I coatomer subunits, which function in vesicle coat assemblyĪnd were previously noted to share weak sequence similarity to condensin subunits, also contain HEAT repeats. #Condensin protein scaffold Activator#Xenopus laevis 13S condensin complex, the Aspergillus BimD and Sordaria macrospora Spo76p proteins, the budding yeast Scc2p protein, and the related Drosophila transcriptional activator Nipped-B. Among the proteins detected were the XCAP-D2 and XCAP-G subunits of the Structural maintenance of chromosome (SMC) proteins. Proteins, including four families of proteins associated with condensins and cohesins, which are nuclear complexes that contain Using sensitive sequence analysis techniques we detected HEAT repeats in various chromosome-associated HEAT repeats correspond to tandemly arranged curlicue-like structures that appear to serve as flexible scaffolding on which ![]()
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