7dm4
Solution structure of ARID4B Tudor domain
Structural highlights
FunctionARI4B_HUMAN Acts as a transcriptional repressor (PubMed:12724404). May function in the assembly and/or enzymatic activity of the Sin3A corepressor complex or in mediating interactions between the complex and other regulatory complexes (PubMed:12724404). Plays a role in the regulation of epigenetic modifications at the PWS/AS imprinting center near the SNRPN promoter, where it might function as part of a complex with RB1 and ARID4A. Involved in spermatogenesis, together with ARID4A, where it functions as a transcriptional coactivator for AR (androgen receptor) and enhances expression of genes required for sperm maturation. Regulates expression of the tight junction protein CLDN3 in the testis, which is important for integrity of the blood-testis barrier. Plays a role in myeloid homeostasis where it regulates the histone methylation state of bone marrow cells and expression of various genes involved in hematopoiesis. May function as a leukemia suppressor (By similarity).[UniProtKB:A2CG63][1] Publication Abstract from PubMedHuman ARID4A and ARID4B are homologous proteins that are important in controlling gene expression and epigenetic regulation but have distinct functions. Previous studies have shown that the N-terminal domain of ARID4A is an unusual interdigitated double Tudor domain with DNA-binding activity. However, how the Tudor domain of ARID4B differs from that of ARID4A remains unknown. Here, we found that the ARID4B Tudor domain has significantly weaker DNA affinity than the ARID4A Tudor domain despite sharing more than 80% sequence identity. Structure determination and DNA titration analysis indicated that the ARID4B Tudor domain is also an interdigitated double Tudor domain with a DNA-binding surface similar to ARID4A. We identified that a residue close to the DNA-binding site of the Tudor domain differs between ARID4A and ARID4B. The Leu50 in ARID4A is Glu50 in ARID4B and the latter forms salt bridges with two lysine residues at the DNA-binding surface. This causes a decrease in the strength of positive charge, thus reducing DNA-binding affinity while significantly increasing protein stability. We also found that a C-terminal extension region enhances the DNA binding affinity of the ARID4B Tudor domain. This C-terminal extension is disordered and contains a positively charged RGR motif, providing an additional DNA-binding site. Finally, sequence and phylogenetic analyses indicated that the residue differences and the presence of the RGR extension region are conserved. These results provide new insight into the functional differences between ARID4A and ARID4B proteins, as well as elucidating the function of the disordered regions in these proteins. Structural basis for the DNA-binding activity of human ARID4B Tudor domain.,Ren J, Yao H, Hu W, Perrett S, Gong W, Feng Y J Biol Chem. 2021 Mar 3:100506. doi: 10.1016/j.jbc.2021.100506. PMID:33675746[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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