AJP - Endocrinology and Metabolism, Vol 253, Issue 1 E81-E89, Copyright © 1987 by American Physiological Society
A translational inhibitor from muscles of diabetic rats: identification as histone H1
N. E. O'Leary, W. B. Mehard, I. R. Cheema, K. Moore and M. G. Buse
A heat- and acid-stable protein fraction that inhibited peptide chain
initiation in rabbit reticulocyte lysates was extracted from frozen,
powdered rat skeletal muscles by stepwise trichloroacetic acid
precipitation. Streptozotocin-induced diabetes increased the inhibitory
activity; this was prevented by insulin therapy. Size-exclusion
high-performance liquid chromatography resolved four inhibitory fractions;
only one was consistently increased (approximately 2-fold) in muscle
extracts from diabetic rats. Polysome profiles of lysates incubated with
this fraction indicated peptide chain initiation inhibition. On sodium
dodecyl sulfate-polyacrylamide gel electrophoresis the purified inhibitory
fraction migrated with apparent Mr 30 and 32 kDa, which on Western blot
immunostained with antisera against histone H1/H1(0). Perchloric acid
extraction of muscle homogenates yielded approximately twofold more H1 from
diabetic than from control rats; yield from diabetics decreased to control
values 5 h after subcutaneous insulin injection. Inclusion of detergent
during homogenization increased H1 yield more from muscles of control than
from diabetic rats and abolished the difference between them. Because H1
affects several biochemical reactions, its facilitated extraction from
insulin-deprived tissues can bias interpretation of studies of insulin
action.
