Biology subjects

Shuman, S.

Publications and source records attributed to Shuman, S..

4 recordsLinked to original sources

bioRxiv2022

Inorganic polyphosphate abets silencing of a sub-telomeric gene cluster in fission yeast

Inorganic polyphosphate (PolyP) is a ubiquitous polymer that plays sundry roles in cell and organismal physiology. Whereas there is evidence for polyphosphate in the cell nucleus, it is unclear whether and how physiological levels of PolyP impact transcriptional regulation in eukarya. To address this issue, we performed transcriptional profiling of fission yeast vtc4{Delta} cells, which lack the catalytic subunit of the Vtc4/Vtc2 polyphosphate polymerase complex and thus have no detectable intracellular PolyP. Deleting Vtc4 elicited the de-repression of four protein-coding genes - SPAC186.04c, gdt1/SPAC186.05, SPAC186.06, and SPAC750.01 - located within a sub-telomeric region of the right arm of chromosome I that is known to be transcriptionally silenced by the TORC2 complex. These sub-telomeric genes were equally de-repressed in vtc2{Delta} cells and in cells expressing polymerase-dead Vtc4, signifying that PolyP synthesis is necessary to abet TORC2-dependent locus-specific gene silencing.

genetics↗

bioRxiv2022

Pleiotropic roles for mycobacterial DinB2 in frameshift and substitution mutagenesis

Translesion synthesis mediated by translesion polymerases is a conserved mechanism of DNA damage tolerance. In bacteria, DinB enzymes are widely distributed promutagenic translesion polymerases. The role of DinBs in mycobacterial mutagenesis was unclear until recent studies revealed a role for mycobacterial DinB1 in substitution and frameshift mutagenesis, overlapping with that of translesion polymerase DnaE2. M. smegmatis encodes two additional DinBs (DinB2 and DinB3) and M. tuberculosis encodes DinB2, but the roles of these polymerases in mycobacterial damage tolerance and mutagenesis is unknown. The biochemical properties of DinB2, including facile utilization of ribonucleotides and 8-oxo-guanine, suggest that DinB2 could be a promutagenic polymerase. Here we examine the effects of DinB2 and DinB3 overexpression in mycobacterial cells. We demonstrate that DinB2 can drive diverse substitution mutations conferring antibiotic resistance. DinB2 induces frameshift mutations in homopolymeric sequences, both in vitro and in vivo. DinB2 switches from less to more mutagenic in the presence of manganese in vitro. This study indicates that DinB2 may contribute to mycobacterial mutagenesis and antibiotic resistance acquisition in combination with DinB1 and DnaE2.

microbiology↗

bioRxiv2022

Distinctive roles of translesion polymerases DinB1 and DnaE2 in diversification of the mycobacterial genome through substitution and frameshift mutagenesis.

Antibiotic resistance of Mycobacterium tuberculosis is exclusively a consequence of chromosomal mutations. Translesion synthesis (TLS) is a widely conserved mechanism of DNA damage tolerance and mutagenesis, executed by translesion polymerases such as DinBs. In mycobacteria, DnaE2 is the only known agent of TLS and the role of DinB polymerases is unknown. Here we demonstrate that mycobacterial DinB1 abets insertion and deletion frameshift mutagenesis in homo-oligonucleotide runs. DinB1 is the primary mediator of spontaneous -1 frameshift mutations in homo-oligonucleotide runs whereas DnaE2 and DinBs are redundant in DNA damage-induced -1 frameshift mutagenesis. DinB1 also promotes missense mutations conferring resistance to rifampicin, with a mutational signature distinct from that of DnaE2. These results highlight DinB1 and DnaE2 as drivers of mycobacterial genome diversification with relevance to antimicrobial resistance and host adaptation.

microbiology↗

bioRxiv2019

Inositol pyrophosphates impact phosphate homeostasis via modulation of RNA 3’ processing and transcription termination

Fission yeast phosphate acquisition genes pho1, pho84, and tgp1 are repressed in phosphate-rich medium by transcription of upstream lncRNAs. Here we show that phosphate homeostasis is subject to metabolite control by inositol pyrophosphates (IPPs), exerted through the 3-processing/termination machinery and the Pol2 CTD code. Increasing IP8 (via Asp1 IPP pyrophosphatase mutation) de-represses the PHO regulon and leads to precocious termination of prt lncRNA synthesis. pho1 de-repression by IP8 depends on cleavage-polyadenylation factor (CPF) subunits, termination factor Rhn1, and the Thr4 letter of the CTD code. pho1 de-repression by mutation of the Ser7 CTD letter depends on IP8. Simultaneous inactivation of the Asp1 and Aps1 IPP pyrophosphatases is lethal, but this lethality is suppressed by mutations of CPF subunits Ppn1, Swd22, Ssu72, and Ctf1 and CTD mutation T4A. Failure to synthesize IP8 (via Asp1 IPP kinase mutation) results in pho1 hyper-repression. Synthetic lethality of asp1{Delta} with Ppn1, Swd22, and Ssu72 mutations argues that IP8 plays an important role in essential 3-processing/termination events, albeit in a manner genetically redundant to CPF. Transcriptional profiling delineates an IPP-responsive regulon composed of genes overexpressed when IP8 levels are increased. Our results establish a novel role for IPPs in cell physiology.

genetics↗