Biology subjects

Flores-Rodriguez, N.

Publications and source records attributed to Flores-Rodriguez, N..

3 recordsLinked to original sources

bioRxiv2024

Anti-phase clustering of regulatory factors shapes gene bursting

Stem cell self-renewal relies on finely tuned transcriptional oscillations of pluripotency genes, yet the sequence by which transcription factors (TFs) govern "on" and "off" states remains unclear. Here, we integrate trimodal single-molecule imaging - SOX2 mobility, Nanog locus diffusion, and real-time Nanog mRNA synthesis using the STREAMING-tag reporter - to visualise endogenous regulatory dynamics in living cells. We identify two SOX2 binding modes linked to transcriptional priming and termination and show coordinated temporal activity of SOX2, OCT4, BRD4, and MED22 at the Nanog locus. Live-cell and fixed-cell measurements reveal that local RNA fluctuations modulate SOX2 visiting-frequency rates. During the active elongation, high nascent enhancer and mRNA levels transiently sequester SOX2 through non-specific interactions, reducing its effective repetitive rebinding and limiting interference with elongating polymerase. After transcript release, declining RNA density permits SOX2 re-engagement, with high-visiting frequency with longer residency and increased locus mobility. These dynamics reveal RNA-dependent feedback that alternately buffers and primes transcriptional re-initiation.

molecular biology↗

bioRxiv2022

Telomerase-independent maintenance of telomere length in a vertebrate

Telomere shortening places a key limitation on cell proliferation1. In all vertebrates explored to date, this limitation is overcome by telomerase-dependent telomere extension. Failure to maintain telomere length results in premature ageing and functional impairments in highly replicative cell populations as telomeres erode2. Alternative lengthening of telomeres (ALT), a telomerase-independent mechanism, compensates for telomere loss in a subset of human cancer cell lines 2. Here, we demonstrate that the highly regenerative newt Pleurodeles waltl lacks telomerase activity, contains telomeres distinct from all known vertebrates in both sequence and structure, and deploys ALT for physiological telomere maintenance. This constitutes the first report of telomerase-independent resolution of the end-replication problem at the whole-organism level within Chordata. One-Sentence SummaryP. waltl telomere biology is distinct amongst vertebrates and uses ALT at the whole-organism level.

molecular biology↗

bioRxiv2018

ESCRT-III accumulates in micronuclei with ruptured nuclear envelopes

1.Micronuclei represent the cellular attempt to compartmentalize DNA to maintain genomic integrity threatened by mitotic errors and genotoxic events. Micronuclei show aberrant nuclear envelopes that collapse, generating damaged DNA and promoting complex genome alterations. However, ruptured micronuclei also provide a pool of cytosolic DNA that stimulates anti-tumour immunity, revealing the complexity of micronuclei impact on tumour progression.\n\nThe ESCRT-III complex ensures nuclear envelope (NE) resealing during late mitosis and NE repair in interphase. Therefore, ESCRT-III activity maybe crucial for maintaining the integrity of other genomic structures enclosed by a nuclear envelope. ESCRT-III activity at the nuclear envelope is coordinated by the subunit CHMP7.\n\nWe show that CHMP7 and ESCRT-III protects against the genomic instability associated with micronuclei formation. Loss of ESCRT-III activity increases the population of micronuclei with ruptured nuclear envelopes, in interphase cells. Surprisingly, ESCRT-III is retained at acentric micronuclei suggesting that ESCRT-III cannot repair these structures. Depletion of CHMP7 expression removes ESCRT-III accumulations at ruptured micronuclei, and removes the population of micronuclei with damaged DNA also containing a sensor for cytosolic DNA.\n\nThus, ESCRT-III activity appears to protect from the consequence of genomic instability in a dichotomous fashion. Membrane repair activity prevents the occurrence of MN with weak envelopes; conversely, aberrant membrane remodelling at micronuclei generates a steady state pool of cytosolic DNA that may contribute to sustaining pro-inflammatory pathways in cancer cells.

cancer biology↗