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D R Roop

Publications and source records attributed to D R Roop.

At least 145 records · Page 8Linked to original sources
PubMed1985

Keratin gene expression in mouse skin tumors and in mouse skin treated with 12-O-tetradecanoylphorbol-13-acetate.

Alterations in the pattern of epidermal differentiation and proliferation occur during mouse skin carcinogenesis. We have used cDNA clones corresponding to the major keratin subunits synthesized in differentiating epidermal cells (Mr 67,000 and 59,000) and in proliferating epidermal cells (Mr 60,000, 55,000, and 50,000) to study changes in keratin gene transcript levels in mouse epidermis exposed to tumor promoters. The same probes were used to characterize the keratin expression patterns in benign and malignant skin tumors. A single topical treatment with 12-O-tetradecanoylphorbol-13-acetate caused a rapid initial decrease in the epidermal transcript levels corresponding to the Mr 67,000 and 59,000 keratin subunits. By 48 h the transcript level for the Mr 67,000 keratin subunit was restored to control values, whereas the transcript levels for the Mr 59,000 subunit returned to control at a slower rate. In contrast, the transcript level for the Mr 55,000 subunit was increased substantially 12- 48 h after treatment, the Mr 50,000 subunit transcript increased to a lesser extent, and the Mr 60,000 subunit message was transiently decreased at 12 h but returned to the level of solvent-treated skin by 24 h. Single exposure to the incomplete tumor promoters 4-O-methyl-12-O-tetradecanoylphorbol-13-acetate, the ionophore A23187, and mezerein induced changes in keratin gene transcripts similar to those of 12-O-tetradecanoylphorbol-13-acetate. The antipromoter fluocinolone acetonide, administered with 12-O-tetradecanoylphorbol-13-acetate, partially inhibited the decrease in the Mr 59,000 and 67,000 transcripts and completely inhibited the increase in the Mr 55,000 transcript. In skin papillomas produced by initiation and promotion, keratin gene expression was similar to normal skin, with the exception of a two-fold increase in the transcript levels for the Mr 55,000 keratin subunit. However, in carcinomas, the transcript levels for the Mr 67,000 and 59,000 subunits were only 1-3% of those observed in untreated mouse epidermis. In concert with other data, the rapid and selective loss of transcripts for differentiation-related keratins after exposure to both complete and incomplete tumor promoters is most consistent with an accelerated rate of maturation in differentiating keratinocytes, resulting in the rapid production of transcript-depleted fully mature squames. The enhanced level of Mr 55,000 transcripts suggests a concomitant increase in the number of all cells or a subset of cells in the proliferative compartment.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1984

Synthetic peptides corresponding to keratin subunits elicit highly specific antibodies.

The presence of common antigenic determinants within all keratin proteins has made difficult the production of antisera which are monospecific for individual keratin subunits. Synthetic peptides corresponding to the carboxyl-terminal amino acid sequences of the mouse 59- and 67-kilodalton keratins were used to produce antibodies which were highly specific for these keratin subunits. This method of antibody production was chosen after examination of amino acid sequence data (which were deduced from the nucleotide sequence of cDNA clones for these and other mouse keratins) revealed that the carboxyl-terminal amino acid sequences of various keratins were unique. Indirect immunofluorescence staining of newborn-mouse skin with these antisera demonstrated that the 59- and 67-kilodalton keratins were only present within the differentiated cells of the epidermis (the suprabasal layers) and not in the undifferentiated cells (the basal layer). These results are consistent with our previous work concerning the expression of these keratin genes at the messenger RNA level (Roop, D. R., Hawley-Nelson, P., Cheng, C. K., and Yuspa, S. H. (1983) Proc. Natl. Acad. Sci. U.S.A. 80, 716-720). Data obtained with the antisera directed against the 67-kilodalton keratin also indicated that the carboxyl-terminal sequences of this subunit were not present in the nonliving layer (the stratum corneum) of the epidermis. This approach should be useful for the production of antisera specific for other keratin subunits as additional sequence information becomes available.

Amino Acid Sequence↗
PubMed1984

The complete cDNA and deduced amino acid sequence of a type II mouse epidermal keratin of 60,000 Da: analysis of sequence differences between type I and type II keratins.

We present the complete nucleotide and deduced amino acid sequences of a mouse epidermal keratin subunit of 60,000 Da. The keratin possesses a central alpha-helical domain of four tracts (termed 1A, 1B, 2A, and 2B) that can form coiled-coils, interspersed by short linker sequences, and has non-alpha-helical terminal domains. This pattern of secondary structure is emerging as common to all intermediate filament subunits. The alpha-helical sequences conform to the type II class of keratins. Accordingly, this is the first type II keratin for which complete sequence information is available, and thus it facilitates elucidation of the fundamental distinctions between type I and type II keratins. It has been observed that type I keratins are acidic and type II keratins are neutral--basic in charge. We suggest that the basis for this empirical correlation between type and charge resides in the respective net charges of the 1A and 2B tracts. Calculations on interchain interactions between charged residues in the alpha-helical domains indicate that this keratin prefers to participate in dimers according to an in-register parallel arrangement. The terminal domains of this keratin possess characteristic glycine-rich sequences, and the carboxyl-terminal domain is highly homologous to that of a human epidermal keratin of 56,000 Da. According to the hypothesis that end-domains are located on the periphery of keratin filaments, we conclude that the corresponding mouse and human keratins are closely related, both structurally and functionally.

Amino Acid Sequence↗
PubMed1983

Complete amino acid sequence of a mouse epidermal keratin subunit and implications for the structure of intermediate filaments.

We have determined the complete primary structure of an intermediate filament subunit, the 59,000 molecular weight subunit of mouse epidermal keratin, from the nucleotide sequence of cDNA clones. The central portion of the sequence forms extended tracts of a coiled-coil alpha-helical conformation. This is flanked at both termini by similar non-alpha-helical sequences that are extremely rich in glycine residues, frequently configured in tandem peptide repeats. Limited chymotryptic digestion of keratin filaments containing this protein suggests a structural organization whereby the terminal glycine-rich sequences protrude from a conserved core structure into which the coiled-coil alpha-helical segments are packed.

Amino Acid Sequence↗
PubMed1983

Keratin gene expression in mouse epidermis and cultured epidermal cells.

The major differentiation products of mouse epidermis are keratins of 40-70 kilodaltons (kDal). We have prepared a library of cDNA clones from total poly(A)+ RNA from newborn mouse epidermis. Clones corresponding to the major in vivo keratins of 55, 59, and 67 kDal have been isolated and characterized. By RNA blot analysis of poly(A)+ RNA from newborn mouse epidermis, we have identified RNA species that are approximately 1,600, 2,000, and 2,400 nucleotides in length and are complementary to the cDNAs for the 55-, 59-, and 67-kDal keratins, respectively. Analysis of RNA from primary cultures of newborn mouse epidermis by this same technique shows greatly reduced levels of these RNAs. Transcripts complementary to all three cloned cDNAs are abundant in 14- to 16-day embryonic and adult mouse skin. Thus, altered expression in culture does not appear to be due to induction of a developmentally programmed switch by placing the cells in culture but instead is due to factors modulating expression within the culture system. Because the 55-, 59-, and 67-kDal keratins are the major proteins in epidermis they probably represent keratin associated with terminal differentiation. The expression data suggest that cultured cells are blocked in expression of differentiation keratins but instead synthesize other keratin family members probably related to cytoskeletal functions.

Animals↗
PubMed1983

Structural features of epidermal keratin filaments reassembled in vitro.

We have studied the structure of epidermal keratin filaments polymerized in vitro, addressing two different levels of organization. First, we have determined the amino acid sequence of a mouse epidermal keratin subunit from the nucleotide sequence of a cDNA clone. The subunit contains a large central region, representing about 50 percent, whose sequence strongly suggests that it assumes a coiled-coil alpha-helical conformation. This is flanked on the amino and carboxyl terminals by long glycine-rich sequences. Second, we have used scanning transmission electron microscopy to study the structure of frozen, unstained filaments. Analyses of such images provides information on the mass per unit length and on the distribution of mass within the filament. These data impose rigorous constraints on possible models for the packing of protofilaments within the filament. Epidermal keratin filaments assembled in vitro are polymorphic; however, the majority of bovine filaments weigh about 37 kD/nm, but most human filaments have masses of only about 27 kD/nm. The filament width is at least 15 nm, substantially more than the generally accepted value of 8 to 10 nm, owing to the existence of low-density mass at the periphery that has not been visualized by conventional microscopic methods. We currently postulate that the alpha-helical regions of the subunits comprise the structural core or backbone of the filament from which at least some of the glycine-rich sequences protrude.

Amino Acid Sequence↗
PubMed1983

Expression of keratin genes in mouse epidermis and normal and malignantly transformed epidermal cells in culture.

Complementary DNA (cDNA) clones constructed to the 55, 59 and 67 kilodalton (K) keratins, the major keratins synthesized in newborn mouse epidermis, were used as molecular hybridization probes to examine the expression of these genes in newborn epidermis and normal and malignantly transformed epidermal cells in culture. Transcripts of these three keratin genes are abundant in newborn epidermis. However, primary cultures of epidermal cells contain very low levels of these RNAs. The decreased expression of these keratin genes in primary cells appears to be due to factors within the culture system. Unlike primary-cell cultures, the malignantly transformed cell line Pam 212 synthesizes keratin proteins and mRNAs similar to newborn epidermis, including the 67 K keratin. However, synthesis of the 67 K keratin in Pam 212 cells is modulated by culture factors. Keratin gene expression in another Pam line, 321, differs from that of Pam 212 cells in that decreased expression of these three keratin genes occurs. These results indicate that keratin genes that are normally expressed in vivo in epidermis may be expressed in malignant epidermal cells under conditions that do not permit expression of these genes in nonmalignant primary epidermal cells.

Animals↗
PubMed1982

Heterogeneous initiation regions for transcription of the chicken ovomucoid gene.

We have identified the 5' termini of ovomucoid RNA transcripts isolated from estrogen stimulated chick oviduct by S1-nuclease mapping. Most of the ovomucoid RNA molecules (88-89%) are initiated at a predominant region which is positioned at about 30 basepairs downstream from a "TATATAT" sequence. However, there is at least one additional initiation region which accounts for 9% of the ovomucoid RNA transcripts. It is located at approximately 80 basepairs further upstream (5') from the major initiation region. DNA sequence data reveal that an AT-rich sequence resembling the "TATA" box is also present 30 nucleotides before this minor region. Our finding provides additional insight into the molecular mechanism involved in the transcription initiation of eucaryotic genes, and indicates that in vivo synthesis of mRNA may not require an absolute site for initiation of transcription.

Animals↗
PubMed1981

Structure and expression of a chicken gene coding for U1 RNA.

We have isolated and sequenced a genomic fragment containing sequences complementary to chicken U1 RNA. The sequence of this genomic U1 gene is completely homologous and colinear with that of chicken U1 RNA. This U1 gene is part of a multigene family (6--10 copies per haploid genome), and these loci do not appear to be closely clustered. Sequences complementary to other snRNAs are not present within the 2.5 kb genomic fragment containing the U1 gene. We have determined that U1 RNA is synthesized by polymerase II; however, a "Hogness box" is not present upstream from its cap site at the position usually observed for mRNA genes. The synthesis of U1 RNA in oviduct nuclei during different states of hormonal induction also appears to be constitutive.

Animals↗
PubMed1980

Evidence that deoxyribonucleic acid sequences flanking the ovalbumin gene are not transcribed.

The transcription of DNA sequences flanking the 5' end and 3' end of the ovalbumin gene was examined. First, various restriction endonuclease fragments corresponding to the 5' and 3' regions of the gene isolated and used as hybridization probes to assay for the presence of transcripts corresponding to these different regions in the chick oviduct nuclear RNA. Very little, if any, of the transcripts corresponding to sequences flanking the 5' and 3' structural sequences of the ovalbumin gene was detected in the steady-state nuclear RNA. Second, RNA was pulse labeled either in isolated nuclei or in an oviduct tissue suspension system and hybridized to DNA filters containing purified fragments of various 5'- and 3'-flanking regions. Our results again demonstrated that RNA was not synthesized from the 5'- and 3'-flanking regions surrounding the gene. Taken together, these results are consistent with the postulate that flanking DNA sequences are not transcribed and that the largest RNA species detected in the nuclear RNA are the initial transcripts.

Animals↗
PubMed1980

Definition of the 5' and 3' ends of transcripts of the ovalbumin gene.

We present data which map the 5' and 3' ends of transcripts of the natural ovalbumin gene. First, hybridization of radiolabeled 5' and 3' fragments of the gene to oviduct nuclear RNA which had been electrophoresed in agarose gels and transferred to DBM paper localized the 5' and 3' ends of precursor molecules and demonstrated that the largest ovalbumin RNA molecules detectable by this method (approximately 7.8 kb) were similar in size to the ovalbumin natural gene. Second, hybridization of end-labeled probes to oviduct nuclear RNA followed by digestion with S1 nuclease and analysis on polyacrylamide gels mapped more precisely the 5' and 3' ends of the precursor molecules, and these termini were coincident with the beginning and end of the structural sequence of the natural gene. These results suggest that the 7.8 kb precursor is likely to be the primary transcript of the ovalbumin gene.

Base Sequence↗
PubMed1979

The ovalbumin gene: transcriptional regulation by estrogen.

De novo synthesis of RNA sequences corresponding to intervening as well as to structural sequences of the ovalbumin gene have been detected in isolated oviduct nuclei. Their presence in the nuclear transcripts and their time course of induction support the hypothesis that transcription of structural and intervening sequences of the natural ovalbumin gene are regulated by steroid hormones. These results are in agreement with out previous demonstration of high-molecular-weight species of ovalbumin RNA in nuclei that contain structural as well as intervening RNA sequences and are thus likely precursors to mature cytoplasmic mRNAov. Analysis of the size of in vivo nuclear RNA by gel electrophoresis under denaturing conditions, revealed that withdrawal of hormone depletes the level of high molecular weight ovalbumin RNA as well as that of nature mRNAov and that readministration of estrogen induces the accumulation of both species. These results are consistent also with transcriptional regulation of the ovalbumin gene. In addition, they rule out the possibility that the rapid accumulation of mature mRNAov after secondard stimulation results from processing of ovalbumin RNA precursors that might have been stored in the withdrawn oviduct. We conclude that steroid hormones exert a primary effect at the level of gene transcription. Following this event, a series of coordinated cellular responses may occur which involve RNA processing, mRNA transport to the cytoplasm, protein synthesis and mRNA degradation. The final consequence of this network of molecular reactions is the induced cellular function inherent to a specific steroid hormone.

Animals↗