title: Side chain independent recognition of aminoacyl adenylates by the Hint1 transcription suppressor.
abstract: Human Hint1 suppresses specific gene transcription by interacting with the transcription factor MITF in mast cells. Hint1 activity is connected to lysyl-tRNA synthetase (LysRS), a member of the universal aminoacyl tRNA synthetase family that catalyzes specific aminoacylation of their cognate tRNAs, through an aminoacyl adenylate (aa-AMP) intermediate. During immune activation, LysRS produces a side-product diadenosine tetraphosphate (Ap(4)A) from the condensation of Lys-AMP with ATP. The pleiotropic signaling molecule Ap(4)A then binds Hint1 to promote activation of MITF-target gene transcription. Earlier work showed that Hint1 can also bind and hydrolyze Lys-AMP, possibly to constrain Ap(4)A production. Because Ap(4)A can result from condensation of other aa-AMP's with ATP, the specificity of the Hint1 aa-AMP-hydrolysis activity is of interest. Here we show that Hint1 has broad specificity for adenylate hydrolysis, whose structural basis we revealed through high-resolution structures of Hint1 in complex with three different aa-AMP analogues. Hint1 recognizes only the common main chain of the aminoacyl moiety, and has no contact with the aa side chain. The α-amino group is anchored by a cation-pi interaction with Trp123 at the C-terminus of Hint1. These results reveal the structural basis for the remarkable adenylate surveillance activity of Hint1, to potentially control Ap(4)A levels in the cell.
authors.affiliation: Department of Cancer Biology, The Scripps Research Institute, Scripps Florida, 130 Scripps Way, Jupiter, Florida 33458, USA.
authors.forename: Jing
authors.initials: J
authors.lastname: Wang
authors.forename: Pengfei
authors.initials: P
authors.lastname: Fang
authors.forename: Paul
authors.initials: P
authors.lastname: Schimmel
authors.forename: Min
authors.initials: M
authors.lastname: Guo
mesh_terms: D000249:Adenosine Monophosphate / Q000031:analogs & derivatives / Q000737:chemistry* / Q000378:metabolism; D018360:Crystallography, X-Ray; D006801:Humans; D006868:Hydrolysis; D008958:Models, Molecular; D009419:Nerve Tissue Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: C063306:HINT1 protein, human; D009419:Nerve Tissue Proteins; D014157:Transcription Factors; D000249:Adenosine Monophosphate