Tj. Gibson et al., EVIDENCE FOR A PROTEIN DOMAIN SUPERFAMILY SHARED BY THE CYCLINS, TFIIB AND RB P107/, Nucleic acids research, 22(6), 1994, pp. 946-952
Cyclins, TFIIB and RB play major roles in cell cycle and/or gene regul
ation. Earlier work has suggested common ancestry for the TFIIB repeat
s and RB pocket B which share 20% sequence identity. We now report tha
t database searches with profiles based on a multiple alignment of cyc
lin core regions (the 'cyclin box') detect the TFIIB repeats with equi
valent scores to divergent cyclins. Several features of the sequences
support the notion of common ancestry: e.g. cyclins A/B, C and D share
similar to 20 - 30% identity but each have similar to 15 - 20% identi
ty with vertebrate TFIIB, showing that conserved cyclin features under
lie the match. These results suggest the presence of a domain superfam
ily, which we term the TR domain, in nuclear regulatory proteins belon
ging to the TFIIB, cyclin and RB families, that has been duplicated ma
ny times during eukaryotic evolution. The TR domain appears to functio
n in protein - protein interactions.