Posts Tagged ‘Mammalian Genome’

Oops: “A Large Proportion of the Mammalian Genome is Functional”

No sooner had Dan Graur finished his talk at the Annual Meeting of the Society for Molecular Biology and Evolution this week on how if ENCODE’s conclusion (that much of our genome is functional rather than junk) is true, then evolution is false, but that ENCODE most assuredly is not true, that the human genome… more

IDENTIFICATION OF MULTIGENE BIOMARKERS

Methods for identifying multigene biomarkers for predicting sensitivity or resistance to an anti-cancer drug of interest, or multigene cancer prognostic biomarkers are disclosed. The disclosed methods are based on the classification of the mammalian ge…

Promoter directionality is controlled by U1 snRNP and polyadenylation signals

Transcription of the mammalian genome is pervasive, but productive transcription outside of protein-coding genes is limited by unknown mechanisms. In particular, although RNA polymerase II (RNAPII) initiates divergently from most active gene promoters, productive elongation occurs primarily in the sense-coding direction. Here we show in mouse embryonic stem cells that asymmetric sequence determinants flanking gene transcription start sites control promoter directionality by regulating promoter-proximal cleavage and polyadenylation. We find that upstream antisense RNAs are cleaved and polyadenylated at poly(A) sites (PASs) shortly after initiation. De novo motif analysis shows PAS signals and U1 small nuclear ribonucleoprotein (snRNP) recognition sites to be the most depleted and enriched sequences, respectively, in the sense direction relative to the upstream antisense direction. These U1 snRNP sites and PAS sites are progressively gained and lost, respectively, at the 5′ end of coding genes during vertebrate evolution. Functional disruption of U1 snRNP activity results in a dramatic increase in promoter-proximal cleavage events in the sense direction with slight increases in the antisense direction. These data suggest that a U1–PAS axis characterized by low U1 snRNP recognition and a high density of PASs in the upstream antisense region reinforces promoter directionality by promoting early termination in upstream antisense regions, whereas proximal sense PAS signals are suppressed by U1 snRNP. We propose that the U1–PAS axis limits pervasive transcription throughout the genome.

Paper Elucidates New Function for Long Non-Coding RNA

Over at ENV, Casey Luskin draws our attention to a new paper in Nature which elucidates new function for long-non-coding RNA. The paper, which can be downloaded here, reports, Most of the mammalian genome is transcribed. This generates a vast repertoire of transcripts that includes protein-coding messenger RNAs, long non-coding RNAs (lncRNAs) and repetitive sequences,… more

Resurrection of endogenous retroviruses in antibody-deficient mice

The mammalian host has developed a long-standing symbiotic relationship with a considerable number of microbial species. These include the microbiota on environmental surfaces, such as the respiratory and gastrointestinal tracts, and also endogenous retroviruses (ERVs), comprising a substantial fraction of the mammalian genome. The long-term consequences for the host of interactions with these microbial species can range from mutualism to parasitism and are not always completely understood. The potential effect of one microbial symbiont on another is even less clear. Here we study the control of ERVs in the commonly used C57BL/6 (B6) mouse strain, which lacks endogenous murine leukaemia viruses (MLVs) able to replicate in murine cells. We demonstrate the spontaneous emergence of fully infectious ecotropic MLV in B6 mice with a range of distinct immune deficiencies affecting antibody production. These recombinant retroviruses establish infection of immunodeficient mouse colonies, and ultimately result in retrovirus-induced lymphomas. Notably, ERV activation in immunodeficient mice is prevented in husbandry conditions associated with reduced or absent intestinal microbiota. Our results shed light onto a previously unappreciated role for immunity in the control of ERVs and provide a potential mechanistic link between immune activation by microbial triggers and a range of pathologies associated with ERVs, including cancer.

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