Biology subjects

Kiso, K.

Publications and source records attributed to Kiso, K..

3 recordsLinked to original sources

bioRxiv2024

ATG5 is dispensable for ATG8ylation of cellular proteins

Protein ATG8ylation refers to a post-translational modification involving covalent attachment of ubiquitin-like autophagy-related protein ATG8 (LC3/GABARAP) to other cellular proteins, with reversal mediated by ATG4 proteases. While lipid ATG8ylation is important for autophagosome formation and mechanistically well-characterized, little is known about the mechanism of protein ATG8ylation. Here, we investigated the conjugation machinery of protein ATG8ylation in CRISPR/Cas9-engineered knockout human cell lines, utilizing a deconjugation-resistant (Q116P G120) form of MAP1LC3B. We report that protein ATG8ylation requires the E1-like activating enzyme ATG7 and E2-like conjugating enzyme ATG3, in common with ATG8 lipidation. However, in contrast, the E3-like ATG12-ATG5-ATG16L1 complex involved in lipidation is dispensable for protein ATG8ylation, since ATG5 knockout cells can form ATG8ylated protein conjugates. Further, we uncover that ATG7 itself is a target of ATG8ylation. Overall, our work provides crucial insight into the mechanism of protein ATG8ylation, distinguishing it from ATG8 lipidation, which will aid investigating its functional role.

cell biology↗

bioRxiv2022

Oncogenic c-Myc activity increases tolerance to proteotoxic and genotoxic stress through regulation of HSF1

Oncogenes, such as c-Myc, enhance growth and proliferative signaling to promote continuous cell cycle divisions, the hallmark of cancer. The inadvertent consequence of this is an increase in cellular stresses. However, whether and how oncogenes can directly contribute to cellular stress tolerance, and how much cancer cells rely on these mechanisms for survival, remains poorly understood. Here we show that c-Mycdependent proteotoxic stress contributes to the generation of genotoxic stress. We reveal an important role for the transcription factor Heat Shock Factor 1 (HSF1) in the tolerance to both these c-Myc-induced stresses. c-Myc upregulates HSF1 directly, by activating its expression, and indirectly, via c-Mycdependent proteotoxic stress activation. In addition to relieving c-Myc-induced proteotoxic and genotoxic stress, HSF1 also enables DNA damage response signalling through{gamma} H2AX. Consequently, acute depletion of HSF1 significantly increases c-Myc-driven genome instability and decreases cell viability. Our results establish that c-Myc-dependent regulation of HSF1 ensures that proteotoxic and genotoxic stress, resulting from c-Myc-induced enhanced growth and proliferation, are compatible with cell survival.

cancer biology↗

bioRxiv2021

Oncogenic c-Myc induces replication stress by increasing cohesins chromatin occupancy

Oncogene-induced replication stress is a major driver of genomic instability in cancer cells, with a central role in both cancer initiation and progression (1). Despite its critical role in cancer development, the mechanisms that lay at the basis of oncogene-induced replication stress remains poorly understood. Here, we investigate the mechanism of c-Myc-induced replication stress. Our data shows that c-Myc induces replication stress by increasing the amount of cohesins bound to chromatin in the G1 phase of the cell cycle. This is independent of previously suggested mechanisms involving deregulation of replication initiation and transcriptional interference. Restoring the amount of chromatin-bound cohesins to control levels, or preventing the accumulation of cohesins at CTCF sites, in cells experiencing oncogenic c-Myc activity prevents replication stress. Increased cohesins chromatin occupancy correlates with a c-Myc-dependent increase in the levels of the cohesion loader Mau2. Preventing c-Myc-induced increase in Mau2 reduces oncogene-induced replication stress. Together our data support a novel mechanism for oncogene-induced replication stress. Since c-Myc activation is a crucial event in many human cancers (2), identifying the mechanisms through which this oncogene promotes replication stress provides critical insights into cancer biology.

cancer biology↗