P. Claus et al., INSECT PROTEINS HOMOLOGOUS TO MAMMALIAN HIGH-MOBILITY GROUP PROTEINS-I Y (HMG-I/Y) - CHARACTERIZATION AND BINDING TO LINEAR AND 4-WAY JUNCTION DNA/, The Journal of biological chemistry, 269(52), 1994, pp. 33042-33048
A chromosomal high mobility group (HMG) protein from an epithelial cel
l line of Chironomus tentans (Diptera) was purified to homogeneity and
chemically characterized. cDNA clones encoding this protein were isol
ated and sequenced. The deduced amino acid sequence revealed a high si
milarity to HMG protein I of mammalia. This insect protein has therefo
re been designated cHMGI. It has a deduced molecular mass of 10,371 kD
a and appears to be a product of a single gene copy. Similarly to mamm
alian HMGI/Y proteins the insect cHMGI protein has three putative DNA-
binding motifs with a sequence K/RXRGRP that are each encoded by one e
xon of the gene. Using synthetic peptides we have shown that the first
and the second moth are necessary for high-affinity binding of the pr
otein to DNA. Protein cHMGI binds preferentially to AT-rich DNA with a
half-saturation value of 1.1 nM. Both cHMGI and human HMGI proteins r
ecognize specifically a four-way junction DNA. We have also purified a
related protein with similar physico-chemical properties from Drosoph
ila melanogaster It, cells. The identification and characterization of
HMGI proteins in insects with polytene chromosomes and with the cytol
ogic and genetic potential of Chironomus and Drosophila opens new poss
ibilities for studying function(s) of this group of chromosomal protei
ns.