S. Kitao et al., Cloning of two new human helicase genes of the RecQ family: Biological significance of multiple species in higher eukaryotes, GENOMICS, 54(3), 1998, pp. 443-452
Two new human DNA helicase genes, RecQ4 and RecQ5, that belong to the RecQ
helicase family were cloned and characterized. The addition of these genes
increases the total to five helicase genes in the human RecQ family, which
includes helicases involved in Bloom and Werner syndromes, the genetic dise
ases manifesting the distinctive but overlapping clinical phenotypes of imm
unodeficiency, premature aging, and an enhanced risk of cancer. The RecQ4 h
elicase is as large as the Bloom (BLM) and Werner (WRN) helicases, and its
gene expression profile is organ-specific, resembling that of BLM helicase.
fn contrast, the RecQ5 helicase has a low molecular weight, similar to the
human progenitor RecQ1 helicase, and is expressed in all the organs examin
ed. All five human helicase genes are expressed in cultured K562 leukemia a
nd fibroblast cells. Synchronized K562 cell cultures showed that the genes
RecQ4 and BLM, and RecQ1 and WRN, seem to be upregulated at the G1/S and G2
/M phases, respectively, of the cell cycle. The biological significance of
multiple species of human RecQ helicases, which are apparently nonessential
for Life but may be related to distinct diseases, is discussed in light of
the fact that unicellular organisms, Like Escherichia coli and yeast, cont
ain only one species of helicase of this particular family. (C) 1998 Academ
ic Press.