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The enzymatic activity of PARP1—which adds chains of (poly-ADP)-ribose (PAR) to proteins—initiates DNA repair by leading to more-accessible chromatin and recruitment of PAR-dependent DNA-repair proteins. New work shows that these PARP1-catalysed functions are redirected by the auxiliary factor HPF1 in cells.
White adipose tissue secretes the small polypeptide hormone leptin, which controls food intake and satiety. Unlike other metabolic hormones such as insulin and glucagon, leptin does not act on the major metabolic organs liver, muscle, and white adipose tissue, but instead exerts its primary function on the central nervous system.
A cardinal rule of DNA replication is to prevent any possibility of pre-replication complexes re-loading during S phase, risking genotoxic over-replication. But can this rule be broken in emergency situations to preserve genome integrity?
The RNA methyltransferase (MTase) METTL1 catalyzes N7-methylguanosine (m7G) modification at position 46 in human transfer RNAs (tRNAs). Its dysregulation drives tumorigenesis in many cancer types. Two papers now reveal the structural basis of this tRNA maturation event.
Recent studies offer new insight on the mechanisms of IP6-mediated HIV-1 capsid assembly. The immature Gag lattice enables enrichment of IP6 into virions, aiding capsid maturation. Structures of capsid protein (CA) assemblies reveal motifs serving as switches modulating the conformations of CA pentamers/hexamers and affect co-factor accessibility.
Sperm flagella of highly divergent eukaryotic species share an architectural plan. Despite their ostensible ultrastructural similarities, mammalian sperm flagella beat with an asymmetric waveform, in contrast to the symmetrical beats of other eukaryotic flagella. Structural findings elucidate the molecular basis for this evolutionary divergence.
AlphaFold2 has already changed structural biology, but its true power may lie in how it changes the way we think about cells and organisms. Two studies broadly assess its utility and limitations in providing structural models to shed light in areas such as mutations, protein–protein interactions, and phosphorylation.
Gene transcription initiation is a highly regulated process in which Pol II and general transcription factors assemble into a pre-initiation complex. Structural studies of yeast and human initiation complexes shed light on the role of the first nucleosome flanking gene promoters in controlling the transcription machinery.
Craspase is newly identified type III CRISPR–Cas system with two major components: the nuclease Cas7-11, and the protease TPR-CHAT. Craspases perform a delicate balancing act between nuclease and protease activity to achieve immune tolerance and defense in bacteria, and show promise as highly regulatable genome-editing tools.
New work on DNA polymerase λ highlights its remarkable flexibility. This fits with the generally adaptable nature of the DNA-repair process in which this enzyme is involved—nonhomologous end-joining—which allows this mechanism to handle diverse types of broken DNA ends in order to restore the duplex structure, albeit with a loss of information at the join.
Nuclear actin polymerization helps facilitate chromosome compartment switches that can shift damaged DNA toward a nuclear environment that is favorable for DNA repair. Yet shifting multiple broken DNA strands together can also increase the likelihood of misjoining of the DNA ends and subsequent formation of translocations.
New research shows that the CoREST complex controls the acquisition of endocrine therapy resistance in estrogen receptor-positive breast cancers. Profiling data show that this resistance transition is accompanied by a functional retargeting of CoREST on chromatin in coordination with cJUN and SWI/SNF (cBAF).
Recent structures of the three-way complex formed by the scaffold protein SHOC2, the small G protein M-RAS and protein phosphatase 1 (PP1) provide a tantalizing insight into the activation of RAF, the oncogenic kinase and downstream effector of RAS that drives cell proliferation and survival.
The mechanisms by which translesion DNA polymerases mediate DNA repair are incompletely understood. A new study shows that Escherichia coli DNA polymerase IV is concentrated at the sites of arrested DNA synthesis by an interaction with SSB, the major single-stranded DNA-binding protein, specifically at stalled but not ongoing replication forks.
New cryo-EM structures of the FANCD2–FANCI complex provide insights into how phosphorylation of FANCI facilitates DNA clamping to prime the complex for monoubiquitination and recruitment of downstream factors in the Fanconi anemia pathway of DNA damage repair.
