How tubulin losing acetylation effect on sun proteins?5 answersTubulin losing acetylation can impact SUN proteins, specifically Mps3 in yeast. Acetylation of tubulin is a post-translational modification that occurs on the luminal surface of microtubules. In yeast, Mps3 is a SUN-domain protein involved in various nuclear functions. The N-terminus of Mps3 is acetylated by the acetyltransferase Eco1/Ctf7, with acetylation sites identified near the transmembrane domain. While acetylation of Mps3 is not essential for growth or spindle pole body (SPB) duplication, it is crucial for accurate sister chromatid cohesion and chromosome recruitment to the nuclear membrane. Therefore, tubulin losing acetylation could potentially disrupt these critical functions of Mps3, affecting nuclear organization and chromosome dynamics in yeast cells.
What is the role of acetylation in cytoskeleton stiffness and mechanotransduction?5 answersAcetylation of α-tubulin plays a crucial role in cytoskeletal stiffness and mechanotransduction. Specifically, acetylated α-tubulin contributes to increased cytoskeletal stiffness and viscoelastic resistance, leading to slowed rates of contraction and relaxation during muscle activity. This modification confers resilience to mechanical stress on microtubules, affecting actomyosin organization and collective cell migration. Moreover, acetylation at lysine 40 of α-tubulin is essential for fibroblast activation, including contraction, migration, and extracellular matrix deposition, thereby promoting skin fibrosis. The upregulation of α-tubulin acetylation under biomechanical stimuli enhances fibrosis by mediating mechanosensitive cellular responses and Yes-associated protein dephosphorylation, highlighting its critical role in matrix stiffness-induced pathological processes.
How many post-translational modifications are discovered to date on histones?4 answersTo date, a wide array of post-translational modifications (PTMs) have been identified on histones. These modifications include methylation, acetylation, phosphorylation, ubiquitination, malonylation, propionylation, butyrylation, crotonylation, lactylation. Additionally, histones can undergo modifications such as isobutyrylation, methacrylation, benzoylation, isonicotinylation, and lactylation, which are newer acylation marks discovered on specific lysine residues. The chemical diversity of these modifications plays a crucial role in histone function within biological systems. Furthermore, histone PTMs contribute to chromatin accessibility and are essential for DNA readout and chromatin remodeling. The intricate network of histone modifications underscores the complexity of the "histone code" and its significance as an epigenetic marker in various cellular processes and diseases.
What does acetylation do to replication forks?4 answersAcetylation of replication forks has various effects on DNA replication. Acetylation of the RRM2 subunit of ribonucleotide reductase (RNR) at K95 disrupts RNR activity and dNTP synthesis, leading to DNA replication fork stalling and reduced tumor cell growth. Acetylation of histone H3 by Rtt109 regulates fork velocity, with N-terminal acetylation slowing replication and K56 acetylation contributing to replication dynamics when N-terminal acetylation is compromised. Deacetylation of H2BK33 and trimethylation of H3K9 in nucleosomes surrounding stalling forks induce chromatin compaction, stabilizing the forks and preventing collapse. Acetylation of newly synthesized histone H4 by Hat1 during replication-coupled chromatin assembly is important for proper processing and assembly of newly synthesized histones, and loss of Hat1 leads to replication fork stalling and degradation of newly synthesized DNA.
What is n terminal acetylation?5 answersN-terminal acetylation is the irreversible addition of an acetyl group to the alpha amino group at the N-terminus of a peptide chain. This modification can disrupt protein interactions, function, localization, degradation, hydrophobicity, or charge. While the biological importance of N-terminal acetylation was initially overlooked, recent studies have shown that it plays a crucial role in controlling gene expression, chromatin function, and cellular processes such as cellular aging, metabolic rewiring, and cancer. In eukaryotic cells, N-terminal acetylation is commonly performed by cytosolic N-terminal acetyltransferases (NATs). In prokaryotes, N-terminal acetylation was once thought to be uncommon, but recent evidence suggests that it may be more common than previously realized. N-terminal acetylation can also be used as a tool for the installation of functional moieties on collagen model peptides, with the length of the acyl group influencing the stability of collagen triple helices. N-terminal acetylation can stabilize proteins in a substrate-specific manner, by competition with N-terminal ubiquitination or other mechanisms independent of protein ubiquitination status.
What are the consequences of loss of acetylation sites in androgen receptors?3 answersLoss of acetylation sites in androgen receptors has several consequences. Mutation of these sites affects the potency and efficacy of androgen-dependent response, particularly on certain promoters such as the Pem promoter. It also leads to delayed ligand-dependent nuclear translocation, misfolding, and aggregation of the receptor. Furthermore, loss of acetylation sites reduces trans-activation of androgen-responsive genes and impairs coactivation by various AR cofactors. The AR acetylation site mutants show reduced responsiveness to trichostatin A and ligand-induced phosphorylation. Additionally, loss of acetylation sites results in increased histone acetylation at AR and non-AR-regulated gene promoters, leading to enhanced AR activity and cell growth in response to all androgens, including weaker adrenal androgens. These findings suggest that acetylation of androgen receptors plays a crucial role in regulating their activity, subcellular distribution, and interaction with other proteins, ultimately influencing the transcriptional regulation of target genes.