HIGH-MOBILITY GROUP PROTEINS CHMG1A, CHMG1B, AND CHMGI ARE DISTINCTLYDISTRIBUTED IN CHROMOSOMES AND DIFFERENTIALLY EXPRESSED DURING ECDYSONE DEPENDENT CELL-DIFFERENTIATION
S. Ghidelli et al., HIGH-MOBILITY GROUP PROTEINS CHMG1A, CHMG1B, AND CHMGI ARE DISTINCTLYDISTRIBUTED IN CHROMOSOMES AND DIFFERENTIALLY EXPRESSED DURING ECDYSONE DEPENDENT CELL-DIFFERENTIATION, Chromosoma, 105(6), 1997, pp. 369-379
The mammalian high mobility group proteins HMGI/Y and HMG1/2 are thoug
ht to play an architectural role in assembly of nucleoprotein structur
es. Counterparts to these proteins have recently been found in the cel
ls of the Dipteran insect Chironomus. In this report we investigate th
e distribution of three abundant HMG proteins in interphase giant chro
mosomes of the midge, Chironomus. By means of the indirect immunofluor
escence technique the cHMG1b and cHMGI proteins were localized in chro
mosomal puffs, suggesting their involvement in the organization of tra
nscriptionally active chromatin. In contrast, the highly abundant prot
ein cHMG1a was rather uniformly distributed in the chromosomes. The cH
MGI protein, but not cHMG1a or cHMG1b, was detected in nucleoli, which
may indicate a role in the transcription of ribosomal genes. The regi
ons of the interphase chromosomes containing AT-rich DNA did not conta
in higher levels of the cHMGI and cHMG1b proteins. A correlation betwe
en the specific location of these proteins in chromatin and their synt
hesis and turnover rates was observed.