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FIG. 5.
Model demonstrating the role of the Paf1 complex in the functional
activation of the Rad6-Bre1 complex in ubiquitination of histone H2B at
promoters. A, the E2 ubiquitin ligase Rad6 is recruited to the
promoter via its E3 ligase Bre1
(26). After the assembly of
the preinitiation complex, the C-terminal domain (CTD) of RNA Pol II
is phosphorylated on serine 5 by Kin28. B, the Paf1 complex
(Paf1c) enters the preinitiation complex and mediates the interaction
among Rad6-Bre1, COMPASS, and RNA Pol II. This interaction is required for the
functional activation of Rad6-Bre1 in ubiquitination of histone H2B on lysine
123. C, after the promoter region is ubiquitinated by Rad6-Bre1, the
complex of RNA Pol II, COMPASS, and the Paf1c enter early elongation as
COMPASS methylates Lys-4 of histone H3 in the early body of the gene.
