The amino acid sequence of actin from chicken skeletal muscle actin and chicken gizzard smooth muscle actin

150

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.

Section: Resultsmentioning

confidence: 65%

Structure, chromosome location, and expression of the human gamma-actin gene: differential evolution, location, and expression of the cytoskeletal beta- and gamma-actin genes.

Erba¹,

Eddy²,

Shows³

et al. 1988

150

“…Prior studies (18,27,30,31,33,45,46) have demonstrated that specific domains within the 3' UT regions of the various isoactins are isotype specific. To analyze these regions of pRVaA-19 and pREyA-11, we generated two subclones designated pRVaA-3' UT-DP and pRE-yA-3' UT-XP, which contain the 3' UT regions of the rat a-vascular and -y-enteric isoactins, respectively.…”

Section: Resultsmentioning

confidence: 99%

“…Even so, previous studies (24,(44)(45)(46) have shown that the y-enteric and a-vascular actins are coexpressed in smooth muscle tissues and that their relative proportions differ from tissue to tissue. Additional studies have demonstrated that the expression of smooth muscle isoactins are regulated by development (22,24), hormones (21), pathological conditions such as atheroscle-rosis (13,36), and specific culture conditions (1,39,41 In an attempt to further define the developmental expression of the two smooth muscle actins, we isolated and characterized a rat -y-enteric smooth muscle actin cDNA designated pREyA-11.…”

mentioning

confidence: 98%

The development expression of the rat alpha-vascular and gamma-enteric smooth muscle isoactins: isolation and characterization of a rat gamma-enteric actin cDNA.

McHugh¹,

Lessard²

1988

We have isolated and characterized two cDNA clones from whole rat stomach, pRVaA-19 and pRE-yA-ll, which are specific for the a-vascular and -y-enteric smooth muscle isoactins, respectively. The rat y-enteric smooth muscle actin contains a single amino acid substitution of a proline for a glutamine at position 359 of the mature peptide when compared with the chicken gizzard y-actin sequence (J. Vandekerckhove and K. Weber, FEBS Lett. 102:219, 1979). Sequence comparisons of the 5' and 3' untranslated (UT) regions of the two smooth muscle actin cDNAs demonstrate that these regions contain no apparent sequence similarities. Additional comparisons of the 5' UT regions of the two smooth muscle actin cDNAs to all other known actin sequences reveal no apparent sequence similarities for the rat -y-enteric isoactin within the 15 base pairs of sequence currently available, while the rat a-vascular isoactin contains two separate sequences which are similar to sequences within the 5' UT regions of the human and chicken a-vascular actin genes. A similar comparison of the 3' UT regions of the two smooth muscle actins demonstrates that the a-vascular isoactins do not contain the high degree of cross-species sequence conservation observed for the other isoactins and that the y-enteric isoactin contains an inverted sequence of 52 nucleotides which is similar to a sequence found within the 3' UT regions of the human, chicken, and rat 0-cytoplasmic isoactins. These observations complicate the apparent cross-species conservation of isotype specificity of these domains previously observed for the other actin isoforms. Northern blot analysis of day 15 rat embryos and newborn, day 19 postbirth, and adult rats demonstrates that the day 15 rat embryo displays low to undetectable levels of smooth muscle isoactin mRNA expression. By birth, the stomach and small intestine show dramatic increases in a-vascular and -y-enteric actin expression. These initially high levels of expression decrease through day 19 to adulthood. In the adult rat, the uterus and aorta differ in their content of smooth muscle isoactin mRNA. These results demonstrate that the y-enteric and a-vascular isoactin mRNAs are coexpressed to various degrees in tissues which contain smooth muscle.

“…These isotypes differ from each other by only a few amino acids; most of these differences are clustered at the amino terminus. Two smooth muscle isotypes (22) and two striated muscle isotypes, a skeletal and a cardiac (21), are integral components of the highly ordered contractile apparatus of muscle fibers. The cytoskeletal actins, i and y, are part of the complex network offilaments that make up the cytoarchitecture of every nonmuscle cell (20).…”

mentioning

confidence: 99%

Human actin genes are single copy for alpha-skeletal and alpha-cardiac actin but multicopy for beta- and gamma-cytoskeletal genes: 3' untranslated regions are isotype specific but are conserved in evolution.

Ponte¹,

Gunning²,

Blau³

et al. 1983

367

165

We have constructed isotype-specific subclones from the 3' untranslated regions of alpha-skeletal, alpha-cardiac, beta-cytoskeletal, and gamma-cytoskeletal actin cDNAs. These clones have been used as hybridization probes to assay the number and organization of these actin isotypes in the human genome. Hybridization of these probes to human genomic actin clones (Engel et al., Proc. Natl. Acad. Sci. U.S.A. 78:4674-4678, 1981; Engel et al., Mol. Cell. Biol. 2:674-684, 1982) has allowed the unambiguous assignment of the genomic clones to isotypically defined actin subfamilies. In addition, only one isotype-specific probe hybridizes to each actin-containing gene, with a single exception. This result suggests that the multiple actin genes in the human genome are not closely linked. Genomic DNA blots probed with these subclones under stringent conditions demonstrate that the alpha-skeletal and alpha-cardiac muscle actin genes are single copy, whereas the cytoskeletal actins, beta and gamma, are present in multiple copies in the human genome. Most of the actin genes of other mammals are cytoplasmic as well. These observations have important implications for the evolution of multigene families.