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Abstract:
Spt6 is an essential transcription elongation factor and
histone chaperone that binds the C-terminal repeat domain
(CTD) of RNA polymerase II. We show here that Spt6 contains
a tandem SH2 domain with a novel structure and CTD-binding
mode. The tandem SH2 domain binds to a serine 2-phosphorylated
CTD peptide in vitro, whereas its N-terminal SH2
subdomain, which we previously characterized, does not. CTD
binding requires a positively charged crevice in the C-terminal
SH2 subdomain, which lacks the canonical phospho-binding
pocket of SH2 domains and had previously escaped detection.
The tandem SH2 domain is apparently required for transcription
elongation in vivo as its deletion in cells is lethal in the
presence of 6-azauracil.
