真核生物rRNA基因的转录调节

核糖体RNA(rRNA）基因的转录直接决定着细胞核糖体的生物发生,而后者与细胞的生长、增殖等行为相适应.研究发现,rRNA基因转录以RNA聚合酶Ⅰ（Pol Ⅰ）为核心,有多种因子参与,并受到多种调控因子的严密调节控制;各调控因子不仅均有自己特异的作用位点,而且又彼此关联、相辅相成.本文在简要介绍真核生物rRNA基因转录基本过程与涉及的主要因子的基础上,重点阐述了rRNA基因转录的主要调节方式,包括ERK、mTOR和JNK等信号转导通路对转录因子磷酸化的影响;转录因子的乙酰化;细胞周期相关因子和其它因子的多种作用方式等. 概括起来看,真核生物rRNA基因转录调节的核心机制是调节转录因子间及转录因子与DNA间的相互作用或影响染色质结构,从而实现对rRNA基因转录的调控,以满足特定生理/病理状况下细胞对rRNA量的要求.     

G1 cyclins regulate proliferation of the budding yeast Saccharomyces cerevisiae.

The eukaryotic cell cycle is regulated at two points, the G1-S and G2-M boundaries. The molecular basis for these regulatory activities has recently been elucidated, in large part by the use of molecular and genetic analyses using unicellular yeast. The molecular characterization of cell-cycle regulation has revealed striking functional conservation among evolutionarily diverse cell types. For many eukaryotic cells, regulation of cell proliferation occurs primarily in the G1 interval. The G1 regulatory step, termed START, requires the activation of a highly conserved p34 protein kinase by association with a functionally redundant family of proteins, the G1 cyclins. Here we review studies using the genetically tractable budding yeast Saccharomyces cerevisiae, which have provided insight into the role of G1 cyclins in the regulation of START.     

Concepts and approaches towards understanding the cellular redox proteome

The physiological activity of a significant subset of cell proteins is modified by the redox state of regulatory thiols. The cellular redox homeostasis depends on the balance between oxidation of thiols through oxygen and reactive oxygen species and reduction by thiol-disulfide transfer reactions. Novel and improved methodology has been designed during recent years to address the level of thiol/disulfide regulation on a genome-wide scale. The approaches are either based on gel electrophoresis or on chromatographic techniques coupled to high end mass spectrometry. The review addresses diagonal 2D-SDS-PAGE, targeted identification of specific redox-interactions, affinity chromatography with thioredoxins and glutaredoxins, gel-based and non-gel based labelling techniques with fluorophores (such as Cy3, Cy5, ICy), radioisotopes, or with isotope-coded affinity tags (ICAT), differential gel electrophoresis (DIGE) and combined fractional diagonal chromatography (COFRADIC). The extended methodological repertoire promises fast and new insight into the intricate regulation network of the redox proteome of animals, bacteria, and plants.