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Telomerase RNA subunit of Ustilago maydis

ABSTRACT: The RNA subunit of telomerase is an essential component whose primary sequence and length are poorly conserved among eukaryotic organisms. The phytopathogen Ustilago maydis is a dimorphic fungus of the Ustilaginaceae family. We analyzed several members of the Ustilaginaceae family to computationally identify the TElomere RNA (TER) gene ter114. To confirm the identity of the TER gene, we disrupted the gene and characterized telomerase-negative mutants. Similar to catalytic TERT mutants, ter114Δ mutants exhibit phenotypes of telomere shortening and low replicative potential. However, ter114Δ mutants had very prolonged replication times, and survivors arose more rapidly in ter114Δ (252 replication rounds) than in their counterpart trt1Δ mutant strains (300 replication rounds). ter114-disrupted mutants were unable to infect maize seedlings in heterozygous crosses and showed defects such as cell cycle arrest and segregation failure. We concluded that ter114, which encodes the TER subunit of the telomerase of U. maydis, could have distinct or more extensive functions than trt1. To further characterize the ter114 gene, we analyze the transcriptomes of both, mRNA nuclear transcripts and nuclear RNA ribo-depleted transcripts of the wild-type strain 521, from the reads of both nuclear fractions, we find four reconstructed transcripts of the ter114 locus, which constitute four isoforms containing the structural domains of TER. The results showed that the transcription start site for the four isoforms is located upstream the start codon of the uncharacterized gene UMAG_03168, while the differential expression analysis showed that the ter114-i4 isoform is up-regulated with respect to the polyadenylated fraction, suggesting that this transcript could correspond to the precursor of the mature form of TER.

ORGANISM(S): Ustilago maydis

PROVIDER: GSE184051 | GEO | 2021/09/17

REPOSITORIES: GEO

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Project description:Genomic instability associated with DNA replication stress is linked to cancer and genetic pathologies in humans. If not properly regulated, replication stress, such as fork stalling and collapse, can be induced at natural replication impediments present throughout the genome. The fork protection complex (FPC) is thought to play a critical role in stabilizing stalled replication forks at several known replication barriers including eukaryotic rDNA genes and the fission yeast mating-type locus. However, little is known about the role of the FPC at other natural impediments including telomeres. Telomeres are considered to be difficult to replicate due to the presence of repetitive GT-rich sequences and telomere-binding proteins. However, the regulatory mechanism that ensures telomere replication is not fully understood. Here, we report the role of the fission yeast Swi1/Timeless, a subunit of the FPC, in telomere replication. Loss of Swi1 causes telomere shortening in a telomerase-independent manner. Our epistasis analyses suggest that heterochromatin and telomere-binding proteins are not major impediments for telomere replication in the absence of Swi1. Instead, repetitive DNA sequences impair telomere integrity in swi1Î mutant cells, leading to the loss of repeat DNA. In the absence of Swi1, telomere shortening is accompanied with an increased recruitment of Rad52 recombinase and more frequent amplification of telomere/subtelomeres, reminiscent of tumor cells that utilize the alternative lengthening of telomeres pathway (ALT) to maintain telomeres. These results suggest that Swi1 ensures telomere replication by suppressing recombination and repeat instability at telomeres. Our studies may also be relevant in understanding the potential role of the FPC in regulation of telomere stability in cancer cells. Genome-wide distributions of Rad52 in wild type and in swi1 deletion in fission yeast The'SP1173_WT ChIP-seq' is an input sample (non-tagged data).

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Telomerase RNA subunit of Ustilago maydis

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