F.A.R.O.G. FORUM, Vol. 5 No. 4

https://digitalcommons.library.umaine.edu/francoamericain_forum/1017/thumbnail.jp

Vortex corrections to universal scaling of magnetic fluctuations in 2D XY model

The vortex contribution to the probability density function of longitudinal magnetization fluctuations is examined in finite 2D XY systems close to the Kosterlitz-Thouless-Berezinskii transition temperature. Within the temperature range studied their relevance is limited to rare fluctuations, where they increase the probability of events exceeding four standard deviations below the mean magnetization.Comment: 6 pages, 4 figures. Refs adde

F.A.R.O.G. FORUM, Vol. 4 No. 1

https://digitalcommons.library.umaine.edu/francoamericain_forum/1054/thumbnail.jp

F.A.R.O.G. FORUM, Vol. 5 No. 6

https://digitalcommons.library.umaine.edu/francoamericain_forum/1018/thumbnail.jp

F.A.R.O.G. FORUM, Vol. 5 No. 7

https://digitalcommons.library.umaine.edu/francoamericain_forum/1019/thumbnail.jp

Multiple Protein Phosphatases Are Required for Mitosis in Drosophila

SummaryBackgroundApproximately one-third of the Drosophila kinome has been ascribed some cell-cycle function. However, little is known about which of its 117 protein phosphatases (PPs) or subunits have counteracting roles.ResultsWe investigated mitotic roles of PPs through systematic RNAi. We found that G2-M progression requires Puckered, the JNK MAP-kinase inhibitory phosphatase and PP2C in addition to string (Cdc25). Strong mitotic arrest and chromosome congression failure occurred after Pp1-87B downregulation. Chromosome alignment and segregation defects also occurred after knockdown of PP1-Flapwing, not previously thought to have a mitotic role. Reduction of several nonreceptor tyrosine phosphatases produced spindle and chromosome behavior defects, and for corkscrew, premature chromatid separation. RNAi of the dual-specificity phosphatase, Myotubularin, or the related Sbf “antiphosphatase” resulted in aberrant mitotic chromosome behavior. Finally, for PP2A, knockdown of the catalytic or A subunits led to bipolar monoastral spindles, knockdown of the Twins B subunit led to bridged and lagging chromosomes, and knockdown of the B′ Widerborst subunit led to scattering of all mitotic chromosomes. Widerborst was associated with MEI-S332 (Shugoshin) and required for its kinetochore localization.ConclusionsWe identify cell-cycle roles for 22 of 117 Drosophila PPs. Involvement of several PPs in G2 suggests multiple points for its regulation. Major mitotic roles are played by PP1 with tyrosine PPs and Myotubularin-related PPs having significant roles in regulating chromosome behavior. Finally, depending upon its regulatory subunits, PP2A regulates spindle bipolarity, kinetochore function, and progression into anaphase. Discovery of several novel cell-cycle PPs identifies a need for further studies of protein dephosphorylation

F.A.R.O.G. FORUM, Vol. 5 No. 3

https://digitalcommons.library.umaine.edu/francoamericain_forum/1016/thumbnail.jp