FIG 1.

The PPM1G phosphatase binds 7SK RNA using its C-terminal Lys-rich domain. (A) Proposed model for the role of PPM1G in the NF-κB transcriptional program. PPM1G is recruited by NF-κB to target genes in response to environmental stimuli, where it dephosphorylates the T-loop of Cdk9 (P-T186), thereby promoting its uncoupling from Hexim1 and its release from the inhibitory, promoter-bound 7SK snRNP complex. In this process, PPM1G subsequently binds 7SK RNA, possibly forming a 7SK-PPM1G snRNP complex lacking P-TEFb. (B) Domain organization of human PPM1G and representation of each domain in the predicted three-dimensional structure. Nt, N-terminal domain; Ac, acidic region; Ct, C-terminal domain; Lys, Lys-rich region. (C) Alignment of PPM1G and Hexim1 Lys-rich regions with their positions indicated in parentheses. (D) Gel shift assays with 7SK RNA and increasing amounts of full-length PPM1G or domains. (E) Binding curves from the gel shifts shown in panel D. (F) Calculations of the apparent dissociation constants (K_d^app) from data in panel E. K_d^app values represent the averages of data from three independent experiments with the standard errors of the means (n = 3). n.d., not determined, because the data set does not enable accurate calculation of the K_d^app values.