Biology subjects

Mostafa, A. M.

Publications and source records attributed to Mostafa, A. M..

2 recordsLinked to original sources

bioRxiv2024

Established Sulfopeptide Tandem Mass Spectrometry Behavior and Sulfotransferase Assays Refute Tyrosine Sulfation as a Histone Mark

Tyrosylprotein sulfotransferases (TPST1 and TPST2) are only known to exist in the Golgi1. Thus, Yu et al.s findings that histone H3 sulfation occurs in the cytosol are surprising. Cytosolic sulfotransferase SULT1B1, which sulfates phenolic small molecules, was proposed to catalyze H3Y99 sulfation with 3'-phosphoadenosine 5'-phosphosulfate (PAPS) as SO3 donor. Bottom-up liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based proteomic analyses were key to this conclusion. Such experiments appear to have been mainly performed following standard protocols, including reduction (reagent unknown), alkylation with iodoacetamide (IAA), and proteolytic digestion prior to nanoflow LC (nanoLC) separation of proteolytic peptides and data-dependent higher energy collision dissociation (HCD) to generate sequence-informative peptide fragments. However, the published HCD MS/MS spectra do not match established sulfopeptide fragmentation behavior. We present reannotation of these spectra and additional experiments that found a lack of evidence to support H3Y99 sulfation.

biochemistry↗

bioRxiv2020

The deacylase SIRT5 supports melanoma viability by regulating chromatin dynamics

Cutaneous melanoma remains the most lethal skin cancer, and ranks third among all malignancies in terms of years of life lost. Despite the advent of immune checkpoint and targeted therapies, only roughly half of patients with advanced melanoma achieves a durable remission. SIRT5 is a member of the sirtuin family of protein deacylases that regulate metabolism and other biological processes. Germline Sirt5 deficiency is associated with mild phenotypes in mice. Here we show that SIRT5 is required for proliferation and survival across all cutaneous melanoma genotypes tested, as well as uveal melanoma, a genetically distinct melanoma subtype that arises in the eye and is incurable once metastatic. Likewise, SIRT5 is required for efficient tumor formation by melanoma xenografts and in an autochthonous mouse Braf;Pten-driven melanoma model. Via metabolite and transcriptomic analyses, we find that SIRT5 is required to maintain histone acetylation and methylation levels in melanoma cells, thereby promoting proper gene expression. SIRT5-dependent genes notably include MITF, a key lineage-specific survival oncogene in melanoma, and the c-MYC proto-oncogene. SIRT5 may represent a novel, druggable genotype-independent addiction in melanoma.

cancer biology↗