The human nuclear protein RbAp48 is a member of the tryptophan/aspartate
(WD) repeat family, which binds to the retinoblastoma (Rb) protein. It also
corresponds to the smallest subunit of the chromatin assembly factor and
is able to bind to the helix 1 of histone H4, taking it to the DNA in replication.
A cDNA homologous to the human gene RbAp48 was isolated from a
Schistosoma mansoni
adult worm library and named SmRbAp48. The full length sequence of SmRbAp48
cDNA is 1036 bp long, encoding a protein of 308 amino acids. The transcript
of SmRbAp48 was detected in egg, cercariae and schistosomulum stages. The
protein shows 84% similarity with the human RbAp48, possessing four WD repeats
on its C-terminus. A hypothetical tridimensional structure for the SmRbAp48
C-terminal domain was constructed by computational molecular modeling using
the b-subunit of the G protein as a model. To further verify a possible
interaction between SmRbAp48 and
S. mansoni
histone H4, the histone H4 gene was amplified from adult worm genomic DNA
using degenerated primers. The gene fragment of SmH4 is 294 bp long, encoding
a protein of 98 amino acids which is 100% identical to histone H4 from
Drosophila melanogaster
.
