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Structure and CTD phosphorylation pattern‐binding specificity of the SRI domain of Set2
Author(s) -
Greenleaf Arno L.,
Phatnani Hemali P.,
Li Ming,
Zhou Pei
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.4.a467-d
Subject(s) - binding site , ctd , chemistry , binding domain , phosphorylation , biophysics , biochemistry , biology , crystallography , oceanography , geology
Set2 is a histone methyltransferase that binds the phosphoCTD of elongating RNAPII via a novel domain termed the SRI (Set2 Rpb1 interacting) domain. We have solved the solution structure of the SRI domain of human Set2, using NMR; and we have characterized its phosphoCTD‐binding specificity, using Biacore. The SRI domain comprises a left‐turned three‐helix bundle distinctly different from other structurally characterized phosphoCTD‐interacting domains. NMR titration / perturbation experiments mapped the binding surface of the SRI domain to helices 1 and 2, and point‐mutagenesis studies identified five residues from those helices that are critical for phosphoCTD binding. Binding specificity studies, using Biacore interaction analyses, showed that the SRI domain binds selectively to doubly‐phosphorylated (on Ser2 and Ser5) CTD repeats; moreover, it requires phosphate groups on four consecutive Ser2/Ser5 residues for maximal binding. The properties of the Set2 SRI domain are consistent with the idea that the CTD of elongating RNAPII carries doubly‐phosphorylated repeats; fittingly, this is the form of repeat most efficiently generated by the major elongation‐related CTD kinase in yeast, CTDK‐I. Supported by NIH grant GM40505.