Biology subjects

Tombline, G.

Publications and source records attributed to Tombline, G..

5 recordsLinked to original sources

bioRxiv2026

Long-lived mammals contain more phosphorylation sites in the SIRT6 C-terminus that enhance PARP1 interaction and resistance to oxidative stress

Sirtuin 6 (SIRT6) is a protein deacetylase and ribosyltransferase that is a vital hub for maintaining epigenetic homeostasis, regulating the transcriptome, and repairing DNA double stranded breaks (DSBs). Comprehensive proteomic profiling of the SIRT6 post-translational landscape, however, remains elusive. The SIRT6 C-terminal domain contains multiple phosphorylation sites. We find that the presence and use of these sites is strongly correlated with maximum lifespan across mammals. Subsequent biochemical and in silico analyses revealed that SIRT6 hyperphosphorylation enhances its interaction with PARP1. Mutating the T294 phosphorylation site in human fibroblasts led to decreased survival after oxidative stress in the phospho-null T294A and improved oxidative stress resistance in the phospho-mimetic T294E. Together, these results suggest SIRT6 C-terminal phosphorylation increases stress resistance through interaction with PARP1, and that this effect has been enhanced by evolution in long-lived species.

molecular biology↗

bioRxiv2025

SIRT6 activator fucoidan extends healthspan and lifespan in aged wild-type mice

SIRT6 is a protein deacylase, deacetylase, and mono-ADP-ribosylase (mADPr) regulating biological pathways important for longevity including DNA repair and silencing of LINE1 retrotransposons. SIRT6 knockout mice die by 30 days of age, whereas SIRT6 overexpression increases lifespan in male mice. Finding safe pharmacological activators of SIRT6 would have clinical benefits. Fucoidan, a polysaccharide purified from brown seaweed, has been identified as an activator of SIRT6 deacetylation activity. Here, we show that fucoidan also activates SIRT6 mADPr activity, which was shown to be elevated in certain human centenarians. Administering fucoidan to aged mice led to a significant increase in median lifespan in male mice. Both male and female mice demonstrated a marked reduction in frailty and epigenetic age. Fucoidan-treated mice showed repression of LINE1 elements suggesting that the beneficial effects of fucoidan are mediated, at least in part, by SIRT6. As brown seaweed rich in fucoidan is a popular food item in South Korea and Japan, countries with the highest life expectancy, we propose that fucoidan supplementation should be explored as a safe strategy for activating SIRT6 and improving human healthspan and lifespan.

molecular biology↗

bioRxiv2024

Hyaluronidase inhibitor delphinidin inhibits cancer metastasis

Cancer remains a formidable global health challenge, with metastasis being a key contributor to its lethality. Abundant high molecular mass hyaluronic acid, a major non-protein component of extracellular matrix, protects naked mole rats from cancer and reduces cancer incidence in mice. Hyaluronidase plays a critical role in degrading hyaluronic acid and is frequently overexpressed in metastatic cancer. Here we investigated the potential of targeting hyaluronidases to reduce metastasis. High throughput screen identified delphinidin, a natural plant compound found in fruits and vegetables, as a potent hyaluronidase inhibitor. Delphinidin-mediated inhibition of hyaluronidase activity led to an increase in high molecular weight hyaluronic acid in cell culture and in mouse tissues, and reduced migration and invasion behavior of breast, prostate, and melanoma cancer cells. Moreover, delphinidin treatment suppressed melanoma metastasis in mice. Our study provides a proof of principle that inhibition of hyaluronidase activity suppresses cancer cell migration, invasion and metastasis. Furthermore, we identify a natural compound delphinidin as a potential anticancer therapeutic. Thus, we have identified a path for clinical translation of the cancer resistance mechanism identified in the naked mole rat.

cancer biology↗

bioRxiv2023

DNA repair and anti-cancer mechanisms in the longest-living mammal: the bowhead whale

At over 200 years, the maximum lifespan of the bowhead whale exceeds that of all other mammals. The bowhead is also the second-largest animal on Earth, reaching over 80,000 kg1. Despite its very large number of cells and long lifespan, the bowhead is not highly cancer-prone, an incongruity termed Petos Paradox2. This phenomenon has been explained by the evolution of additional tumor suppressor genes in other larger animals, supported by research on elephants demonstrating expansion of the p53 gene3-5. Here we show that bowhead whale fibroblasts undergo oncogenic transformation after disruption of fewer tumor suppressors than required for human fibroblasts. However, analysis of DNA repair revealed that bowhead cells repair double strand breaks (DSBs) and mismatches with uniquely high efficiency and accuracy compared to other mammals. The protein CIRBP, implicated in protection from genotoxic stress, was present in very high abundance in the bowhead whale relative to other mammals. We show that CIRBP and its downstream protein RPA2, also present at high levels in bowhead cells, increase the efficiency and fidelity of DNA repair in human cells. These results indicate that rather than possessing additional tumor suppressor genes as barriers to oncogenesis, the bowhead whale relies on more accurate and efficient DNA repair to preserve genome integrity. This strategy which does not eliminate damaged cells but repairs them may be critical for the long and cancer-free lifespan of the bowhead whale.

cancer biology↗

bioRxiv2020

The genome of North American beaver provides insights into the mechanisms of its longevity and cancer resistance

The North American beaver (Castor canadensis) is an exceptionally long-lived and cancer-resistant rodent species, and thus an excellent model organism for comparative genomic studies of longevity. Here, we utilize a significantly improved beaver genome assembly to assess evolutionary changes in gene coding sequences, copy number, and expression. We found that the beaver Aldh1a1, a stem cell marker gene encoding an enzyme required for detoxification of ethanol and aldehydes, is expanded (~10 copies vs. two in mouse and one in human). We also show that the beaver cells are more resistant to ethanol, and beaver liver extracts show higher ability to metabolize aldehydes than the mouse samples. Furthermore, Hpgd, a tumor suppressor gene, is uniquely duplicated in the beaver among rodents. Our evolutionary analysis identified beaver genes under positive selection which are associated with tumor suppression and longevity. Genes involved in lipid metabolism show positive selection signals, changes in copy number and altered gene expression in beavers. Several genes involved in DNA repair showed a higher expression in beavers which is consistent with the trend observed in other long-lived mammals. In summary, we identified several genes that likely contribute to beaver longevity and cancer resistance, including increased ability to detoxify aldehydes, enhanced tumor suppression and DNA repair, and altered lipid metabolism.

genomics↗