Partial sequence homologies between cytoskeletal proteins, c-myc, Rous sarcoma virus and adenovirus proteins, transducin, and β- and γ-crystallins

1985 ◽  
Vol 5 (2) ◽  
pp. 167-174 ◽  
Author(s):  
M. James ◽  
C. Crabbe
Keyword(s):  
Sequence Homology ◽  
Rous Sarcoma Virus ◽  
Cytoskeletal Proteins ◽  
Partial Sequence ◽  
Virus Protein ◽  
Rous Sarcoma ◽  
Sequence Homologies ◽  
Significant Homology ◽  
Sarcoma Virus ◽  
Simian Sarcoma Virus

Computer based sequence comparisons indicate partial sequence homology between human c-myc, Rous sarcoma virus, adenovirus 7, and simian sarcoma virus proteins and the cytoskeletal proteins desmin, keratin and vimentin. In addition, sections of the oncogene proteins showed partial but significant homology to α and β subunits of transducin, γ-II and β-BP crystallins showed partial but significant homology to the cytoskeletal proteins keratin, vimentin, desmin, α and β-tubulin, and to adenovirus 7 and simian sarcoma virus transforming gene proteins. β-BP crystallin showed partial but significant homology to Rous sarcoma virus protein, and to α and y subunits of transducin. Both crystallins showed partial sequence homology to the GTP-binding protein elongation factor TU from Escherichia coli. These sequence homologies suggest a link between the mechanisms of normal lens cell differentiation, involving modifications to the cytoskeleton and subsequent changes to the pattern of protein synthesis, and mechanisms of neoplastic transformation. Furthermore the transducin-like region on β-crystallin may be important for its interaction with lens membranes and the maintenance of short-range order for lens transparency.

scholarly journals Organization of pp60src and selected cytoskeletal proteins within adhesion plaques and junctions of Rous sarcoma virus-transformed rat cells.

1981 ◽  
Vol 89 (3) ◽  
pp. 525-535 ◽  
Author(s):  
K Shriver ◽  
L Rohrschneider
Keyword(s):  
Intermediate Filament ◽  
Rous Sarcoma Virus ◽  
Cytoskeletal Proteins ◽  
Intermediate Filament Protein ◽  
Rous Sarcoma ◽  
Adhesion Junctions ◽  
Src Gene ◽  
Sarcoma Virus ◽  
Adhesion Plaques ◽  
Filament Protein

The localization of pp60src within adhesion structures of epithelioid rat kidney cells transformed by the Schmidt-Ruppin strain of Rous sarcoma virus was compared to the organization of actin, alpha-actinin, vinculin (a 130,000-dalton protein), tubulin, and the 58,000-dalton intermediate filament protein. The adhesion structures included both adhesion plaques and previously uncharacterized adhesive regions formed at cell-cell junctions. We have termed these latter structures "adhesion junctions." Both adhesion plaques and adhesion junctions were identified by interference-reflection microscopy and compared to the location of pp60src and the various cytoskeletal proteins by double fluorescence. The results demonstrated that the src gene product was found within both adhesion plaques and the adhesion junctions. In addition, actin, alpha-actinin, and vinculin were also localized within the same pp60src-containing adhesion structures. In contrast, tubulin and the 58,000-dalton intermediate filament protein were not associated with either adhesion plaques or adhesion junctions. Both adhesion plaques and adhesion junctions were isolated as substratum-bound structures and characterized by scanning electron microscopy. Immunofluorescence revealed that pp60src, actin, alpha-actinin, and vinculin were organized within specific regions of the adhesion junctions. Heavy accumulations of actin and alpha-actinin were found on both sides of the junctions with a narrow gap of unstained material at the midline, whereas pp60src stain was more intense in this central region. Antibody to vinculin stained double narrow lines defining the periphery of the junctional complexes but was excluded from the intervening region. In addition, the distribution of vinculin relative to pp60src within adhesion plaques suggested an inverse relationship between the presence of these two proteins. Overall, these results establish a close link between the src gene product and components of the cytoskeleton and implicate the adhesion plaques and adhesion junctions in the mechanism of Rous sarcoma virus-induced transformation.

scholarly journals Multiple tropomyosin polypeptides in chicken embryo fibroblasts: differential repression of transcription by Rous sarcoma virus transformation.

1984 ◽  
Vol 4 (9) ◽  
pp. 1823-1833 ◽  
Author(s):  
M Hendricks ◽  
H Weintraub
Keyword(s):  
Molecular Weight ◽  
Rous Sarcoma Virus ◽  
Chicken Embryo ◽  
Cytoskeletal Proteins ◽  
Rous Sarcoma ◽  
Muscle Tropomyosin ◽  
Sarcoma Virus ◽  
Virus Transformation ◽  
Embryo Fibroblasts ◽  
Chicken Embryo Fibroblasts

We have found that cytoskeletal extracts of cultured chicken embryo fibroblasts contain at least seven distinct polypeptides (two major and five minor) which cross-react with antiserum to chicken smooth muscle tropomyosin. These polypeptides range in apparent molecular weight from 31,000 to 47,000, and each is encoded by mRNAs which specifically hybridize to cloned muscle tropomyosin cDNAs. These nonmuscle tropomyosin species and their respective mRNAs are electrophoretically distinct from those of chicken skeletal muscle and appear by genomic DNA blotting to comprise a part of a multigene tropomyosin family. In Rous sarcoma virus-transformed chicken embryo fibroblasts, synthesis of the tropomyosins is differentially repressed such that the synthesis of the major species (cp35 and cp33, cytoskeletal proteins of molecular weight 35,000 and 33,000, respectively) and three minor species is drastically reduced, whereas the synthesis of two of the minor species (cp32 and cp31) remains essentially unchanged. Analysis of cellular mRNA and runoff nuclear transcription experiments indicate that the repression of tropomyosin synthesis by Rous sarcoma virus transformation occurs at the level of transcription. This repression of tropomyosin synthesis is partially mimicked in normal chicken embryo fibroblasts during incubation in high-NaCl medium, a condition in which chicken embryo fibroblasts acquire many characteristics of transformed cells.

scholarly journals Second-Site Suppressors of Rous Sarcoma Virus CA Mutations: Evidence for Interdomain Interactions

2001 ◽  
Vol 75 (15) ◽  
pp. 6850-6856 ◽  
Author(s):  
J. Bradford Bowzard ◽  
John W. Wills ◽  
Rebecca C. Craven
Keyword(s):  
Rous Sarcoma Virus ◽  
Alpha Helix ◽  
Single Amino Acid ◽  
Virus Protein ◽  
Terminal Domain ◽  
Rous Sarcoma ◽  
Single Amino Acid Change ◽  
Sarcoma Virus ◽  
Carboxy Terminal ◽  
Ca Protein

ABSTRACT The capsid (CA) protein, the major structural component of retroviruses, forms a shell that encases the ribonucleoprotein complex in the virion core. The most conserved region of CA, ∼20 amino acids of the major homology region (MHR), lies within the carboxy-terminal domain of the protein. Structural and sequence similarities among CA proteins of retroviruses and the CA-like proteins of hepatitis B virus and various retrotransposons suggest that the MHR is involved in an aspect of replication common to these reverse-transcribing elements. Conservative substitutions in this region of the Rous sarcoma virus protein were lethal due to a severe deficiency in reverse transcription, in spite of the presence of an intact genome and active reverse transcriptase in the particles. This finding suggests that the mutations interfered with normal interactions among these constituents. A total of four genetic suppressors of three lethal MHR mutations have now been identified. All four map to the sequence encoding the CA-spacer peptide (SP) region of Gag. The F167Y mutation in the MHR was fully suppressed by a single amino acid change in the alpha helix immediately downstream of the MHR, a region that forms the major dimer interface in human immunodeficiency virus CA. This finding suggests that the F167Y mutation indirectly interfered with dimerization. The F167Y defect could also be repaired by a second, independent suppressor in the C-terminal SP that was removed from CA during maturation. This single residue change, which increased the rate of SP cleavage, apparently corrected the F167Y defect by modifying the maturation pathway. More surprising was the isolation of suppressors of the R170Q and L171V MHR mutations, which mapped to the N-terminal domain of the CA protein. This finding suggests that the two domains, which in the monomeric protein are separated by a flexible linker, must communicate with each other at some unidentified point in the viral replication cycle.

Multiple tropomyosin polypeptides in chicken embryo fibroblasts: differential repression of transcription by Rous sarcoma virus transformation

1984 ◽  
Vol 4 (9) ◽  
pp. 1823-1833
Author(s):  
M Hendricks ◽  
H Weintraub
Keyword(s):  
Molecular Weight ◽  
Rous Sarcoma Virus ◽  
Chicken Embryo ◽  
Cytoskeletal Proteins ◽  
Rous Sarcoma ◽  
Muscle Tropomyosin ◽  
Sarcoma Virus ◽  
Virus Transformation ◽  
Embryo Fibroblasts ◽  
Chicken Embryo Fibroblasts

We have found that cytoskeletal extracts of cultured chicken embryo fibroblasts contain at least seven distinct polypeptides (two major and five minor) which cross-react with antiserum to chicken smooth muscle tropomyosin. These polypeptides range in apparent molecular weight from 31,000 to 47,000, and each is encoded by mRNAs which specifically hybridize to cloned muscle tropomyosin cDNAs. These nonmuscle tropomyosin species and their respective mRNAs are electrophoretically distinct from those of chicken skeletal muscle and appear by genomic DNA blotting to comprise a part of a multigene tropomyosin family. In Rous sarcoma virus-transformed chicken embryo fibroblasts, synthesis of the tropomyosins is differentially repressed such that the synthesis of the major species (cp35 and cp33, cytoskeletal proteins of molecular weight 35,000 and 33,000, respectively) and three minor species is drastically reduced, whereas the synthesis of two of the minor species (cp32 and cp31) remains essentially unchanged. Analysis of cellular mRNA and runoff nuclear transcription experiments indicate that the repression of tropomyosin synthesis by Rous sarcoma virus transformation occurs at the level of transcription. This repression of tropomyosin synthesis is partially mimicked in normal chicken embryo fibroblasts during incubation in high-NaCl medium, a condition in which chicken embryo fibroblasts acquire many characteristics of transformed cells.

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