Ca. Ouzounis et Nc. Kyrpides, PARALLEL ORIGINS OF THE NUCLEOSOME CORE AND EUKARYOTIC TRANSCRIPTION FROM ARCHAEA, Journal of molecular evolution, 42(2), 1996, pp. 234-239
Computational sequence analysis of 10 available archaean histone-like
proteins has shown that this family is not only divergently related to
the eukaryotic core histones H2A/B, H3, and H4, but also to the centr
al domain of subunits A and C of the CCAAT-binding factor (CBF), a tra
nscription factor associated with eukaryotic promoters. Despite the lo
w sequence identity, it is unambiguously shown that the core histone f
old shares a common evolutionary history. Archaean histones and the tw
o CBF families show a remarkable variability in contrast to eukaryotic
core histones. Conserved residues shared between families are identif
ied, possibly being responsible for the functional versatility of the
core histone fold. The H4 subfamily is most similar to archaean protei
ns and may be the progenitor of the other core histones in eukaryotes.
While it is not clear whether archaean histones are more actively inv
olved in transcription regulation, the present observations link two p
rocesses, nucleosomal packing and transcription in a unique way. Both
these processes, evidently hybrid in Archaea, have originiated before
the ermergence of the eukaryotic cell.