Structure, chromosome location, and expression of the human gamma-actin gene: differential evolution, location, and expression of the cytoskeletal beta- and gamma-actin genes.
The accumulation of the cytoskeletal beta- and gamma-actin mRNAs was determined in a variety of mouse tissues and organs. The beta-isoform is always expressed in excess of the gamma-isoform. However, the molar ratio of beta- to gamma-actin mRNA varies from 1.7 in kidney and testis to 12 in sarcomeric muscle to 114 in liver. We conclude that, whereas the cytoskeletal beta- and gamma-actins are truly coexpressed, their mRNA levels are subject to differential regulation between different cell types. The human gamma-actin gene has been cloned and sequenced, and its chromosome location has been determined. The gene is located on human chromosome 17, unlike beta-actin which is on chromosome 7. Thus, if these genes are also unlinked in the mouse, the coexpression of the beta- and gamma-actin genes in rodent tissues cannot be determined by gene linkage. Comparison of the human beta- and gamma-actin genes reveals that noncoding sequences in the 5'-flanking region and in intron III have been conserved since the duplication that gave rise to these two genes. In contrast, there are sequences in intron III and the 3'-untranslated region which are not present in the beta-actin gene but are conserved between the human gamma-actin and the Xenopus borealis type 1 actin genes. Such conserved noncoding sequences may contribute to the coexpression of beta- and gamma-actin or to the unique regulation and function of the gamma-actin gene. Finally, we demonstrate that the human gamma-actin gene is expressed after introduction into mouse L cells and C2 myoblasts and that, upon fusion of C2 cells to form myotubes, the human gamma-actin gene is appropriately regulated.
Erba
H P
HP
MEDIGEN Project, Department of Medicine, Stanford University School of Medicine, California.
Eddy
R
R
Shows
T
T
Kedes
L
L
Gunning
P
P
D000199:Actins / Q000235:genetics*; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D002874:Chromosome Mapping; D002886:Chromosomes, Human, Pair 17; D002897:Chromosomes, Human, Pair 7; D003599:Cytoskeleton / Q000378:metabolism*; D004262:DNA Restriction Enzymes; D005796:Genes; D006801:Humans; D007668:Kidney / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D009132:Muscles / Q000378:metabolism; D009710:Nucleotide Mapping; D009928:Organ Specificity; D012333:RNA, Messenger / Q000235:genetics; D013737:Testis / Q000378:metabolism; D014158:Transcription, Genetic
D000199:Actins; D012333:RNA, Messenger; D004262:DNA Restriction Enzymes