The cohesin ring uses its hinge to organize DNA using non-topological as well as topological mechanisms

As predicted by the notion that sister chromatid cohesion is mediated by entrapment of sister DNAs inside cohesin rings, there is perfect correlation between co-entrapment of circular minichromosomes and sister chromatid cohesion. In most cells where cohesin loads without conferring cohesion, it does so by entrapment of individual DNAs. However, cohesin with a hinge domain whose positively charged lumen is neutralized loads and moves along chromatin despite failing to entrap DNAs. Thus, cohesin engages chromatin in non-topological, as well as topological, manners. Since hinge mutations, but not Smc-kleisin fusions, abolish entrapment, DNAs may enter cohesin rings through hinge opening. Mutation of three highly conserved lysine residues inside the Smc1 moiety of Smc1/3 hinges abolishes all loading without affecting cohesin’s recruitment to CEN loading sites or its ability to hydrolyze ATP. We suggest that loading and translocation are mediated by conformational changes in cohesin’s hinge driven by cycles of ATP hydrolysis

Paleomagnetic results from two hydrothermally altered units in the superior province

Two problems of Precambrian palcomagnctism, namely the scarcity of well-dated palcopolcs for this geological era, and the aggravating effects of retrograde hydrothermal alteration on the rocks from which the scanty palcomagnetic record available derives, arc evaluated by the study of two specific test-cases in the northcentral and northwestern Superior Province. The fonnations studied arc: the unaltered granitic batholiths and hydrothermally altered supracrustal units of the Archean Red Lake Grcenstone Belt (northwestern Ontario), a major gold-producing region: and the Kcwccnawan-agc carbonatites and Archean anorthositcs of the Kapuskasing Structural Zone (KSZ, northcentral Ontario), an early Proterozoic belt that has been hypothesized as a cross-section of the continental crust…Ph.D

Memorias IX Congreso Geológico Venezolano (4)

Memorias IX Congreso Geológico Venezolano (4