6ksf
From Proteopedia
Crystal Structure of ALKBH1 bound to 21-mer DNA bulge
Structural highlights
FunctionALKB1_MOUSE Dioxygenase that acts as on nucleic acids, such as DNA and tRNA (PubMed:27027282, PubMed:27745969). Requires molecular oxygen, alpha-ketoglutarate and iron (PubMed:27027282). A number of activities have been described for this dioxygenase, but recent results suggest that it mainly acts as on tRNAs and mediates their demethylation or oxidation depending on the context and subcellular compartment (By similarity). Mainly acts as a tRNA demethylase by removing N(1)-methyladenine from various tRNAs, with a preference for N(1)-methyladenine at position 58 (m1A58) present on a stem loop structure of tRNAs (PubMed:27745969). Acts as a regulator of translation initiation and elongation in response to glucose deprivation: regulates both translation initiation, by mediating demethylation of tRNA(Met), and translation elongation, N(1)-methyladenine-containing tRNAs being preferentially recruited to polysomes to promote translation elongation (By similarity). In mitochondrion, specifically interacts with mt-tRNA(Met) and mediates oxidation of mt-tRNA(Met) methylated at cytosine(34) to form 5-formylcytosine (f(5)c) at this position (By similarity). mt-tRNA(Met) containing the f(5)c modification at the wobble position enables recognition of the AUA codon in addition to the AUG codon, expanding codon recognition in mitochondrial translation (By similarity). Specifically demethylates DNA methylated on the 6th position of adenine (N(6)-methyladenosine) DNA (PubMed:27027282). N(6)-methyladenosine (m6A) DNA is present at some L1 elements in embryonic stem cells and probably promotes their silencing (PubMed:27027282). Demethylates mRNAs containing N(3)-methylcytidine modification (By similarity). Also able to repair alkylated single-stranded DNA by oxidative demethylation, but with low activity (By similarity). Also has DNA lyase activity and introduces double-stranded breaks at abasic sites: cleaves both single-stranded DNA and double-stranded DNA at abasic sites, with the greatest activity towards double-stranded DNA with two abasic sites (By similarity). DNA lyase activity does not require alpha-ketboglutarate and iron and leads to the formation of an irreversible covalent protein-DNA adduct with the 5' DNA product (By similarity). DNA lyase activity is not required during base excision repair and class switch recombination of the immunoglobulin heavy chain during B lymphocyte activation (PubMed:23825659). May play a role in placental trophoblast lineage differentiation (PubMed:18163532).[UniProtKB:Q13686][1] [2] [3] [4] Publication Abstract from PubMedN(6)-methyladenine (N(6)-mA) of DNA is an emerging epigenetic mark in mammalian genome. Levels of N(6)-mA undergo drastic fluctuation during early embryogenesis, indicative of active regulation. Here we show that the 2-oxoglutarate-dependent oxygenase ALKBH1 functions as a nuclear eraser of N(6)-mA in unpairing regions (e.g., SIDD, Stress-Induced DNA Double Helix Destabilization regions) of mammalian genomes. Enzymatic profiling studies revealed that ALKBH1 prefers bubbled or bulged DNAs as substrate, instead of single-stranded (ss-) or double-stranded (ds-) DNAs. Structural studies of ALKBH1 revealed an unexpected "stretch-out" conformation of its "Flip1" motif, a conserved element that usually bends over catalytic center to facilitate substrate base flipping in other DNA demethylases. Thus, lack of a bending "Flip1" explains the observed preference of ALKBH1 for unpairing substrates, in which the flipped N(6)-mA is primed for catalysis. Co-crystal structural studies of ALKBH1 bound to a 21-mer bulged DNA explained the need of both flanking duplexes and a flipped base for recognition and catalysis. Key elements (e.g., an ALKBH1-specific alpha1 helix) as well as residues contributing to structural integrity and catalytic activity were validated by structure-based mutagenesis studies. Furthermore, ssDNA-seq and DIP-seq analyses revealed significant co-occurrence of base unpairing regions with N(6)-mA in mouse genome. Collectively, our biochemical, structural and genomic studies suggest that ALKBH1 is an important DNA demethylase that regulates genome N(6)-mA turnover of unpairing regions associated with dynamic chromosome regulation. Mammalian ALKBH1 serves as an N(6)-mA demethylase of unpairing DNA.,Zhang M, Yang S, Nelakanti R, Zhao W, Liu G, Li Z, Liu X, Wu T, Xiao A, Li H Cell Res. 2020 Mar;30(3):197-210. doi: 10.1038/s41422-019-0237-5. Epub 2020 Feb, 12. PMID:32051560[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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