Part 4. Please read the following article and answer the following questions |source: Modified from Nucleic Acids Research,49 (1), 177-189 (2021)] Short-chain acylations of lysine residues in eukaryotic proteins are recognized as essential posttranslational chemical modifications(PTMs) that regulate cellular processes from transcription. cell cycle. metabolism. to signal transduction. Lysine butyrylation wasinitially discovered as a normal straight chain butyrylation (Knbu). Fere we report its structural isomer, branched chain butyrylation.i.c. Iysine isobutyrylation (Kibu). existing as a new PTM on nuclear histones. Uniquely, isobutyryl-CoA is derived from valinecatabolism and branched chain fatty acid oxidation which is distinct from the metabolism of n-butyryl-CoA. Several histoneacctyltransferases were found to possess iysine isobutyryltransferase activity in vitro, especially p300 and HAT1. Transfection andwestern blot experiments showed that p300 regulated histone isobutyrylation levels in the cell. We resoived the X-ray crystalstructures of HATI in complex with isobutyryl-CoA that gleaned an atomic level insight into HAT-catalyzed isobutyrylation.RNA-Seq profiling revealed that isobutyrate greatiy afficcted the expression of genes associated with many pivotal biologicalpathways. Together, our findings identify Kibu as a novel chemical modification mark in histones and suggest its extensive role inregulating epigenetics and cellular physiology.
【題組】15. What is NOT regulated by posttranslational chemical modifications (PTMs)? (3%)
(A) acylations of lysine residues
(B) signal transduction
(C) cell cycle
(D) gene expression