SLIDE, the Protein Interacting Domain of Imitation Switch Remodelers, Binds DDT-Domain Proteins of Different Subfamilies in Chromatin Remodeling Complexes

The Imitation Switch （ISWI） type adenosine triphosphate （ATP）-dependent chromatin remodeling factors are conserved proteins in eukaryotes, and some of them are known to form stable remodeling complexes with members from a family of proteins, termed DDT-domain proteins. Although it is well documented that ISWIs play important roles in different biological processes in many eukaryotic species, the molecular basis for protein interactions in ISWI complexes has not been fully addressed. Here, we report the identification of interaction domains for both ISWI and DDT-domain proteins. By analyzing CHROMATIN REMODELING11 （CH R11） and RINGLET1 （RLT1）, an Arabidopsis thaliana ISWI （AtlSWI） and AtDDT-domain protein, respectively, we show that the SLIDE domain of CHR11 and the DDT domain together with an adjacent sequence of RLT1 are responsible for their binding. The Arabidopsis genome contains at least 12 genes that encode DDT-domain proteins, which could be grouped into five subfamilies based on the sequence similarity. The SLIDE domain of AtlSWI is able to bind members from different AtDDT subfamilies. Moreover, a human ISWI protein SNF2H is capable of binding AtDDT-domain proteins through its SLIDE domain, suggesting that binding to DDT-domain proteins is a conserved biochemical function for the SLIDE domain of ISWIs in eukaryotes.

Coordinated control of oligodendrocyte development by extrinsic and intrinsic signaling cues

Oligodendrocytes, the myelin-forming cells for axon ensheathment in the central nervous system, are critical for maximizing and maintaining the conduction velocity of nerve impulses and proper brain function. Demyeli- nation caused by injury or disease together with failure of myelin regeneration disrupts the rapid propagation of action potentials along nerve fibers, and is associated with acquired and inherited disorders, including dev- astating multiple sclerosis and leukodystrophies. The molecular mechanisms of oligodendrocyte myelination and remyelination remain poorly understood. Recently, a series of signaling pathways including Shh, Notch, BMP and Wnt signaling and their intracellular effectors such as Olig1/2, Hesl/5, Smads and TCFs, have been shown to play important roles in regulating oligodendrocyte development and myelination. In this review, we summarize our recent understanding of how these signaling pathways modulate the progression of oligoden- drocyte specification and differentiation in a spatiotemporally-specific manner. A better understanding of the complex but coordinated function of extracellular signals and intracellular determinants during oligodendrocyte development will help to devise effective strategies to promote myelin repair for patients with demyelinating diseases.

DNA End Resection:Facts and Mechanisms

DNA double-strand breaks（DSBs）,which arise following exposure to a number of endogenous and exogenous agents,can be repaired by either the homologous recombination（HR）or non-homologous end-joining（NHEJ） pathways in eukaryotic cells.A vital step in HR repair is DNA end resection,which generates a long 30single-stranded DNA（ss DNA） tail that can invade the homologous DNA strand.The generation of 30 ss DNA is not only essential for HR repair,but also promotes activation of the ataxia telangiectasia and Rad3-related protein（ATR）.Multiple factors,including the MRN/X complex,C-terminal-binding protein interacting protein（Ct IP）/Sae2,exonuclease 1（EXO1）,Bloom syndrome protein（BLM）/Sgs1,DNA2 nuclease/helicase,and several chromatin remodelers,cooperate to complete the process of end resection.Here we review the basic machinery involved in DNA end resection in eukaryotic cells.