Project description:Herpesvirus late promoters activate gene expression after viral DNA synthesis has begun. Alphaherpesviruses utilize a viral immediate-early protein to do this, whereas beta- and gammaherpesviruses primarily use a 6-member set of viral late-acting transcription factors (LTF) that are drawn to a TATT sequence in the late promoter. The betaherpesvirus, human cytomegalovirus (HCMV), produces three immediate-early 2 protein isoforms, IE2-86, IE2-60, IE2-40, in late infection, but whether they activate late viral promoters is unknown. Here, we quickly degrade the IE2 proteins in late infection and analyze effects on transcription using customized PRO-Seq and computational methods combined with multiple validation methods. We discover that the IE2 proteins selectively drive RNA Pol II transcription initiation at a subset of viral early-late and late promoters common to different HCMV strains, but do not substantially affect Pol II transcription of the 9,942 expressed host genes. Most of the IE2-activated viral late infection promoters lack the TATT sequence bound by the HCMV UL87-encoded LTF. The HCMV TATT-binding protein is not mechanistically involved in late RNA expression from the IE2-activated TATT-less UL83 (pp65) promoter, as it is for the TATT-containing UL82 (pp71) promoter. While antecedent viral DNA synthesis is necessary for transcription from the late infection viral promoters, continued viral DNA synthesis is unnecessary. We conclude that the IE2 proteins target a distinct subset of late infection HCMV promoters for transcription initiation by RNA Pol II. Commencement of viral DNA replication renders the HCMV genome late promoters susceptible to late-acting viral transcription factors, which do not appreciably affect host transcription during this late time.
Project description:The importance of unanchored Ub in innate immunity has been shown only for a limited number of unanchored Ub-interactors. We investigated what additional cellular factors interact with unanchored Ub and whether unanchored Ub plays a broader role in innate immunity. To identify unanchored Ub-interacting factors from murine lungs, we used His-tagged recombinant poly-Ub chains as bait. These chains were mixed with lung tissue lysates and protein complexes were isolated with Ni-NTA beads. Sample elutions were subjected to mass spectrometry (LC-MSMS) analysis.
Project description:The role of mitochondria dynamics and its molecular regulators remains largely unknown during naïve-to-primed pluripotent cell interconversion. Here we report that mitochondrial MTCH2 is a regulator of mitochondrial fusion, essential for the naïve-to-primed interconversion of murine embryonic stem cells (ESCs). During this interconversion, wild-type ESCs elongate their mitochondria and slightly alter their glutamine utilization. In contrast, MTCH2-/- ESCs fail to elongate their mitochondria and to alter their metabolism, maintaining high levels of histone acetylation and expression of naïve pluripotency markers. Importantly, enforced mitochondria elongation by the pro-fusion protein Mitofusin (MFN) 2 or by a dominant negative form of the pro-fission protein dynamin-related protein (DRP) 1 is sufficient to drive the exit from naïve pluripotency of both MTCH2-/- and wild-type ESCs. Taken together, our data indicate that mitochondria elongation, governed by MTCH2, plays a critical role and constitutes an early driving force in the naïve-to-primed pluripotency interconversion of murine ESCs.
Project description:We characterized the role of the conserved murine cytomegalovirus (MCMV) gene M79. Using a recombinant MCMV virus carrying a tagged M79 coding sequence, we showed that M79 encoded a protein (pM79) which was expressed at late times of infection and localized to nuclear viral replication compartments. M79 transcription was largely dependent on viral DNA synthesis but was markedly stimulated by pM79, suggesting a positive feedback loop. To investigate its role, we created the recombinant virus SMin79, in which the M79 coding sequence was disrupted by an 88-nt insertion. We subsequently repaired the mutation to generate marker-rescued virus SMrev79. While SMrev79 grew efficiently in fibroblasts, SMin79 failed to produce infectious progeny but was rescued by pM79 expression in trans. During SMin79 infection, representative viral immediate early and early gene products, as well as viral DNA, accumulated efficiently. Formation of viral replication compartments also appeared normal. Pulsed field gel electrophoresis analysis indicated that the overall structure of replicating viral DNA was indistinguishable in cells infected with SMin79 compared to that with wild type virus. However, the accumulation of viral products for late gene M55 was severely compromised. Viral oligonucleotide tiled array analysis revealed that the accumulation of many late transcripts, defined by their sensitivity to viral DNA synthesis inhibitor phosphonoacetic acid, was markedly reduced by pM79 mutation. This study extends our previous work to suggest that cytomegaloviruses use a conserved mechanism to promote transcription at late stages of infection, and that pM79 regulates expression of a subset of viral DNA synthesis-dependent transcripts. This study consists of 4 unreplicated samples. RNA from Mock-infected, WT infected, WT infected in the presence of PAA, and a mutant M79 version of MCMV.