scholarly journals Suggestive evidence for two different mucin genes in rat intestine

1993 ◽  
Vol 294 (2) ◽  
pp. 391-399 ◽  
Author(s):  
I A Khatri ◽  
G G Forstner ◽  
J F Forstner

In the present report we describe the isolation and sequence of a partial cDNA (M2-798) for a rat intestinal mucin designated M2. A rat intestinal lambda ZAP II cDNA library was screened using a polyclonal antiserum which was prepared against deglycosylated high-molecular-mass glycopeptides of the purified mucin. Mucin cDNA clones were found to contain tandem repeats of 18 nt which encoded a threonine- and proline-rich peptide having a consensus sequence of TTTPDV. This is the same sequence reported recently by Gum, Hicks, Lagace, Byrd, Toribara, Siddiki, Fearney, Lamport and Kim [(1991) J. Biol. Chem. 266, 22733-22738] for a rat intestinal cDNA called RMUC 176. A novel feature present in the cDNA M2-798 is a 246 nt unique region at the 3′ end which encodes a hydrophobic sequence of 82 amino acids. RNA blots probed with M2-798 cDNA produced a single hybridization band between 7.5 and 9.0 kb in rat small intestine and colon. An identical hybridization pattern was obtained with a PCR-generated cDNA probe corresponding solely to the unique hydrophobic region of M2-798, demonstrating that this region is encoded by the authentic M2 mRNA. Our data suggest that the unique region of M2 has the potential to be either a transmembrane region, or a domain which mediates hydrophobic interactions of the mucin with other molecules. Since we have previously reported another rat intestinal cDNA which encodes the C-terminus of a mucin-like peptide (MLP) [Xu, Wang, Huan, Cutz, Forstner and Forstner (1992) Biochem. J. 286, 335-338], we wished to discover whether M2 was encoded by the same gene. RNA blotting experiments with probes specific for M2 and MLP showed different mRNAs for each. The message for M2 (7.5-8.5 kb) was smaller than that for MLP (> 9.5 kb) and, unlike MLP, gave no signal in human colonic LS174T cells. The results of DNA blots probed with M2-798 and an MLP-probe suggest that M2 and MLP are likely to be single-copy genes. It would appear therefore that normal rat intestine, like human intestine, may express two different mucin genes.

1995 ◽  
Vol 308 (1) ◽  
pp. 89-96 ◽  
Author(s):  
B S Turner ◽  
K R Bhaskar ◽  
M Hadzopoulou-Cladaras ◽  
R D Specian ◽  
J T LaMont

Polyclonal antibodies raised to deglycosylated pig gastric mucin were used to screen a cDNA library constructed with pig stomach mucosal mRNA. Immunocytochemistry indicated that the antibody recognizes intracellular and secreted mucin in surface mucous cells of pig gastric epithelium. A total of 70 clones producing proteins immunoreactive to this antibody were identified, two of which (PGM-2A,9B) were fully sequenced from both ends. Clone PGM-9B hybridized to a polydisperse mRNA (3-9 kb) from pig stomach, but not liver, intestine or spleen, nor to mRNA from human, mouse, rabbit or rat stomach. Sequence analysis indicated that PGM-9B encodes 33 tandem repeats of a 16-amino-acid consensus sequence rich in serine (46%) and threonine (17%). Using the restriction enzyme MwoI, which has a single target site in the repeat, it was demonstrated that PGM-9B consists entirely of this tandem repeat. Southern-blot analysis indicated that the repeat region is contained in a 20 kb HindIII-EcoRI fragment, and BamHI digestion suggested that most of the repeats are contained in a 10 kb fragment. In situ hybridization with an antisense probe to PGM-9B showed an intense signal in the entire gastric gland. Clone PGM-2A also contains the same repeat sequence as 9B, but, in addition, has a 64-amino-acid-long non-repeat region at its 5′ end. Interestingly the non-repeat region of PGM-2A has five cysteine residues, the arrangement of which is identical with that reported for human intestinal mucin gene MUC2.


1998 ◽  
Vol 274 (5) ◽  
pp. L750-L761 ◽  
Author(s):  
Tae-Suk Kim ◽  
Chandra Dodia ◽  
Xi Chen ◽  
Brian B. Hennigan ◽  
Mahendra Jain ◽  
...  

A clone for a rat acidic Ca2+-independent phospholipase A2(aiPLA2) was isolated from a cDNA library prepared from rat granular pneumocytes with a probe based on the human aiPLA2 sequence (T. S. Kim, C. S. Sundaresh, S. I. Feinstein, C. Dodia, W. R. Skach, M. K. Jain, T. Nagase, N. Seki, K. Ishikawa, N. Nomura, and A. B. Fisher. J. Biol. Chem. 272: 2542–2550, 1997). In addition, a consensus sequence for mouse aiPLA2 was constructed from several mouse cDNA clones in the GenBank and dbEST databases. Each sequence codes for a 224-amino acid protein with 88% identity of the amino acids among the three species and conservation of a putative lipase motif (GDSWG). Translation of mRNA produced from the rat clone in a wheat germ system resulted in expression of PLA2 activity with properties similar to those of the human enzyme, i.e., acidic pH optimum and Ca2+ independence. The localization of aiPLA2 in rat tissues was studied with the human cDNA probe, polyclonal and monoclonal antibodies, and aiPLA2activity. aiPLA2 is present in the lung as evidenced by high levels of mRNA and protein expression and by enzymatic activity that is inhibited by anti-PLA2 antibody and by the transition state analog 1-hexadecyl-3-trifluoroethylglycero- sn-2-phosphomethanol (MJ33). Immunocytochemistry showed the presence of aiPLA2 in alveolar type II cells, alveolar macrophages, and bronchiolar epithelium. In the brain, heart, liver, kidney, spleen, and intestine, aiPLA2 mRNA content was <50% of that in the lung, immunoreactive protein was not detectable, and enzymatic activity was not inhibited by MJ33 or aiPLA2 antibody. These results show marked enrichment of aiPLA2in the lung compared with the other organs and suggest translational control of aiPLA2 expression.


Genome ◽  
1998 ◽  
Vol 41 (2) ◽  
pp. 148-153 ◽  
Author(s):  
Monique Abadon ◽  
Eric Grenier ◽  
Christian Laumond ◽  
Pierre Abad

An AluI satellite DNA family has been cloned from the entomopathogenic nematode Heterorhabditis indicus. This repeated sequence appears to be an unusually abundant satellite DNA, since it constitutes about 45% of the H. indicus genome. The consensus sequence is 174 nucleotides long and has an A + T content of 56%, with the presence of direct and inverted repeat clusters. DNA sequence data reveal that monomers are quite homogeneous. Such homogeneity suggests that some mechanism is acting to maintain the homogeneity of this satellite DNA, despite its abundance, or that this repeated sequence could have appeared recently in the genome of H. indicus. Hybridization analysis of genomic DNAs from different Heterorhabditis species shows that this satellite DNA sequence is specific to the H. indicus genome. Considering the species specificity and the high copy number of this AluI satellite DNA sequence, it could provide a rapid and powerful tool for identifying H. indicus strains.Key words: AluI repeated DNA, tandem repeats, species-specific sequence, nucleotide sequence analysis.


1992 ◽  
Vol 12 (1) ◽  
pp. 164-171
Author(s):  
M J Matunis ◽  
W M Michael ◽  
G Dreyfuss

At least 20 major proteins make up the ribonucleoprotein (RNP) complexes of heterogeneous nuclear RNA (hnRNA) in mammalian cells. Many of these proteins have distinct RNA-binding specificities. The abundant, acidic heterogeneous nuclear RNP (hnRNP) K and J proteins (66 and 64 kDa, respectively, by sodium dodecyl sulfate-polyacrylamide gel electrophoresis) are unique among the hnRNP proteins in their binding preference: they bind tenaciously to poly(C), and they are the major oligo(C)- and poly(C)-binding proteins in human HeLa cells. We purified K and J from HeLa cells by affinity chromatography and produced monoclonal antibodies to them. K and J are immunologically related and conserved among various vertebrates. Immunofluorescence microscopy with antibodies shows that K and J are located in the nucleoplasm. cDNA clones for K were isolated, and their sequences were determined. The predicted amino acid sequence of K does not contain an RNP consensus sequence found in many characterized hnRNP proteins and shows no extensive homology to sequences of any known proteins. The K protein contains two internal repeats not found in other known proteins, as well as GlyArgGlyGly and GlyArgGlyGlyPhe sequences, which occur frequently in many RNA-binding proteins. Overall, K represents a novel type of hnRNA-binding protein. It is likely that K and J play a role in the nuclear metabolism of hnRNAs, particularly for pre-mRNAs that contain cytidine-rich sequences.


1993 ◽  
Vol 13 (9) ◽  
pp. 5710-5724
Author(s):  
E DesJardins ◽  
N Hay

Transcription of the human proto-oncogene c-myc is governed by two tandem principal promoters, termed P1 and P2. In general, the downstream promoter, P2, is predominant, which is in contrast to the promoter occlusion phenomenon usually observed in genes containing tandem promoters. A shift in human c-myc promoter usage has been observed in some tumor cells and in certain physiological conditions. However, the mechanisms that regulate promoter usage are not well understood. The present studies identify regulators which are required to promote transcription from both human c-myc promoters, P1 and P2, and have a role in determining their relative activities in vivo. A novel regulatory region located 101 bp upstream of P1 was characterized and contains five tandem repeats of the consensus sequence CCCTCCCC (CT element). The integrity of the region containing all five elements is required to promote transcription from P1 and for maximal activity from P2 in vivo. A single copy of this same element, designated CT-I2, also appears in an inverted orientation 53 bp upstream of the P2 transcription start site. This element has an inhibitory effect on P1 transcription and is required for P2 transcription. The transcription factor Sp1 was identified as the factor that binds specifically to the tandem CT elements upstream of P1 and to the CT-I2 element upstream of P2. In addition, the recently cloned zinc finger protein ZF87, or MAZ, was also able to bind these same elements in vitro. The five tandem CT elements can be functionally replaced by a heterologous enhancer that only in the absence of CT-I2 reverses the promoter usage, similar to what is observed in the translocated c-myc allele of Burkitt's lymphoma cells.


1993 ◽  
Vol 264 (6) ◽  
pp. G1169-G1176 ◽  
Author(s):  
E. B. Rand ◽  
A. M. Depaoli ◽  
N. O. Davidson ◽  
G. I. Bell ◽  
C. F. Burant

cDNA clones encoding rat GLUT5-small intestinal facilitative hexose transporter were isolated from a jejunum library by cross-hybridization with a human GLUT5 cDNA probe. The cDNA sequence indicates that rat GLUT5 is composed of 502 amino acids and has 81.5% amino acid identity and 87.3% similarity with the sequence of human GLUT5. Expression of synthetic rat GLUT5 mRNA in Xenopus oocytes showed that rat GLUT5 was able to mediate the uptake of fructose and, to a lesser extent, of glucose. RNA blotting studies showed that GLUT5 mRNA was present in rat small intestine, kidney, and brain. Although GLUT5 mRNA is expressed in human testis, adipose tissue, and skeletal muscle, it could not be detected by RNA blotting in these rat tissues. Developmental studies showed low levels of GLUT5 mRNA in rat small intestine and kidney during the prenatal period with a rapid induction of GLUT5 expression occurring postnatally. In situ hybridization studies of GLUT5 mRNA expression in the small intestine revealed differential expression along the crypt-villus axis with the highest levels of mRNA being in the midvillus region. In addition, there was quantitatively more GLUT5 mRNA detected in the proximal as opposed to the distal small intestine.


1992 ◽  
Vol 263 (4) ◽  
pp. L413-L429 ◽  
Author(s):  
M. C. Rose

Mucins, major components of the extracellular mucus blanket that protect and lubricate mammalian epithelia, are high-molecular-mass glycoconjugates (154 to > or = 7,000 kDa) with hundreds of oligosaccharide chains in O-glycosidic linkages to a protein backbone. The apparent expression of more than one type of oligosaccharide core structure in mucins isolated from pathological material may reflect either inherent limitations in analysis, disease-related alterations in parameters affecting glycosylation and post-translational modifications (e.g., nucleotide-sugar concentrations, expression of specific glycosyltransferases, rates of transport through the endoplasmic reticulum and Golgi) or the activation of mucin protein genes that are more highly expressed in disease states with different glycosylation patterns. Recent studies have revealed the existence of a family of at least four human mucin proteins; MUC1, MUC2, MUC3, MUC4, each of which contains a variable number of tandem repeats that differ in sequence and size. Full-length sequences of cDNA clones encoding human mucin proteins are currently available only for MUC1 which, in contrast to most airway and intestinal mucins, is membrane associated and not secreted. Current information on mucin oligosaccharides and proteins is reviewed herein. More detailed knowledge of the protein and oligosaccharide structures of mucins will be important in identifying specific role(s) in health and disease, i.e., in the physiological functions of mucus.


1992 ◽  
Vol 12 (1) ◽  
pp. 164-171 ◽  
Author(s):  
M J Matunis ◽  
W M Michael ◽  
G Dreyfuss

At least 20 major proteins make up the ribonucleoprotein (RNP) complexes of heterogeneous nuclear RNA (hnRNA) in mammalian cells. Many of these proteins have distinct RNA-binding specificities. The abundant, acidic heterogeneous nuclear RNP (hnRNP) K and J proteins (66 and 64 kDa, respectively, by sodium dodecyl sulfate-polyacrylamide gel electrophoresis) are unique among the hnRNP proteins in their binding preference: they bind tenaciously to poly(C), and they are the major oligo(C)- and poly(C)-binding proteins in human HeLa cells. We purified K and J from HeLa cells by affinity chromatography and produced monoclonal antibodies to them. K and J are immunologically related and conserved among various vertebrates. Immunofluorescence microscopy with antibodies shows that K and J are located in the nucleoplasm. cDNA clones for K were isolated, and their sequences were determined. The predicted amino acid sequence of K does not contain an RNP consensus sequence found in many characterized hnRNP proteins and shows no extensive homology to sequences of any known proteins. The K protein contains two internal repeats not found in other known proteins, as well as GlyArgGlyGly and GlyArgGlyGlyPhe sequences, which occur frequently in many RNA-binding proteins. Overall, K represents a novel type of hnRNA-binding protein. It is likely that K and J play a role in the nuclear metabolism of hnRNAs, particularly for pre-mRNAs that contain cytidine-rich sequences.


1993 ◽  
Vol 294 (2) ◽  
pp. 589-593 ◽  
Author(s):  
J Cheng ◽  
K J Macon ◽  
J E Volanakis

The RD gene, initially defined in the mouse, has been mapped between the Bf and C4A genes in the human major histocompatibility complex class III region. Using the mouse cDNA as a probe, we isolated and sequenced human RD cDNA clones. The composite nucleotide sequence consisted of 1301 nucleotides, excluding a poly(A) tail at the 3′ end. It contained a single open reading frame encoding a polypeptide of 380 amino acid residues with a calculated molecular mass of 42274 Da. The most striking structural feature of the deduced amino acid sequence is a region consisting entirely of 24 tandem repeats of an Arg-Asp (or Glu) dipeptide. The human RD cDNA was expressed in Escherichia coli as a fusion protein with glutathione S-transferase and used to produce antisera in rabbits. Western blot analysis and immunoprecipitation of lysates of biosynthetically labelled HeLa cells indicated that RD is a 44 kDa nuclear protein.


1989 ◽  
Vol 109 (6) ◽  
pp. 2575-2587 ◽  
Author(s):  
S Piñol-Roma ◽  
M S Swanson ◽  
J G Gall ◽  
G Dreyfuss

Immediately after the initiation of transcription in eukaryotes, nascent RNA polymerase II transcripts are bound by nuclear proteins resulting in the formation of heterogeneous nuclear ribonucleoprotein (hnRNP) complexes. hnRNP complexes from HeLa cell nuclei contain greater than 20 major proteins in the molecular mass range of 34,000-120,000 D. Among these are the previously described A, B, and C groups of proteins (34,000-43,000 D) and several larger, and as yet uncharacterized, proteins. Here we describe the isolation and characterization of a novel hnRNP protein termed the L protein (64-68 kD by mobility in SDS-polyacrylamide gels). Although L is a bona fide component of hnRNP complexes, it also appears to be a different type of hnRNP protein from those previously characterized. A considerable amount of L is found outside hnRNP complexes, and monoclonal antibodies to the L protein also strongly stain unidentified discrete nonnucleolar structures, in addition to nucleoplasm, in HeLa cell nuclei. Interestingly, the same antibodies stain the majority of nonnucleolar nascent transcripts from the loops of lampbrush chromosomes in the newt, but the most intense staining is localized to the landmark giant loops. The L protein is the first protein of giant loops identified so far, and antibodies to it thus provide a useful tool with which to study these unique RNAs. In addition, isolation and sequencing of cDNA clones for the L protein from human cells predicts a glycine- and proline-rich protein of 60,187 D, which contains two 80 amino acid segments only distantly related to the RNP consensus sequence-type RNA-binding domain. The L protein, therefore, is a new type of hnRNP protein.


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