Anaphase is initiated by proteolysis rather than by the inactivation of maturation-promoting factor

Article Abstract:

Frog extracts that organize mitotic spindles were used to determine the process that activates sister chromatid separation. Maturation-promoting factor (MPF) inactivation is not necessary to start anaphase because the addition of a nondegradable version of cyclin B fails to obstruct sister chromatid separation, though it stops MPF inactivation. The dose-dependent retardation of MPF inactivation and sister chromatid separation results from the addition of an N-terminal fragment cyclin that functions as a specific competitor for cyclin degradation. The proteins other than the identified cyclins should be degraded to dissolve the connection between sister chromatids because even in extracts having only nondegradable versions of cyclin, the N-terminal cyclin fragment impairs chromosome separation. Ubiquitin-mediated proteolysis is required to start anaphase, because it is impaired by methylated ubiquitin which also retards sister chromatid separation.

Analysis, Causes of, Influence, Cell cycle, Proteolysis, Anaphase

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MAP kinases in meiosis

Article Abstract:

The meiotic cycle is characterized by a number of features, including the proliferation of somatic cells, pathways similar with the growth factors utilized to push arrested cells and MAP kinase modules with various type of roles. These modules, which prevents oocytes from escaping into interphases, phosphorylates and activates MAP kinase kinases but do not activate Cdc2. Moreover, MAP kinase control the remainder of meiosis, wherein oocytes do not return to interphase and the nuclear envelop does not reform.

Meiosis, Oocytes, Oocyte donation, Cell hybridization

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Chromosome and low copy plasmid segregation in E. coli: Visual evidence for distinct mechanisms

Article Abstract:

DNA segregation in E. coli has been investigated by the insertion of multiple lac operator seqeuences into a chromosome near origin of replication, in the hisC gene and P1 and F plasmids. Origin of replication was found to be specifically sited at or near cell poles. P1 and F were sited at the cell center and moved rapidly on duplication.

Genetic aspects, DNA, Observations, Escherichia coli, Plasmids

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