Genes encoding proteins with homologous contiguous repeat sequences are highly expressed in the serous cells of the rat submandibular gland

An abundant class of secreted salivary polypeptides is characterized by the presence of identical and contiguous repeats of amino acid sequences within the polypeptide chains, and includes the proline-rich proteins. We discovered a new family of contiguous repeat polypeptides (CRPs) that is related to the proline-rich proteins but contains little proline. Analysis of salivary mRNAs and liver DNA by molecular cloning, DNA sequence determinations, and Northern and Southern blot hybridization revealed several closely related CRP mRNAs and at least 10 CRP-related genes. We further analyzed two CRP mRNAs of 850 and 920 nucleotides and the gene encoding the larger CRP mRNA. The two mRNAs contain the same 69-base repeats in their coding regions and are identical in their 5'- and 3'-untranslated tracts. However, they differ in the number of contiguous repeats (four versus five) and a segment at the 3' end of the coding region which encodes closely related but unique COOH termini of the CRPs. These structural features suggest a recent gene conversion. The CRP gene analyzed is divided into three exons that encode (i) 5'-untranslated tract and signal sequence, (ii) secreted polypeptide, and (iii) 3'-untranslated tract, respectively. CRP mRNA contains two open reading frames. The longer open reading frame encodes a CRP precursor with a signal sequence of 17 amino acids, four to five contiguous repeats of 23 amino acids, and a variable COOH region that begins with two segments related to the contiguous repeats. Immunochemical analysis of salivary gland slices with antisera raised against peptides corresponding to two regions of the larger open reading frame revealed intense staining only of the serous cells of the submandibular glands. 35S-Labeled oligonucleotides complementary to CRP mRNA specifically hybridized to the same cells.     

Characterization of the major mRNAs transcribed from the genes for glycoprotein B and DNA-binding protein ICP8 of herpes simplex virus type 1.

The structural genes encoding the herpes simplex virus type 1 glycoprotein B and the major DNA-binding protein ICP8 have been mapped previously within the EcoRI-F restriction fragment (map coordinates 0.314 to 0.420) of the viral genome. In this study the mRNAs transcribed from these DNA sequences were identified by hybridization selection of 32P-labeled RNA and by Northern blot analysis of polyadenylated cytoplasmic RNA. A 3.4-kilobase RNA was the major mRNA homologous to the DNA sequences between coordinates 0.343 and 0.386 in which mutations in the glycoprotein B gene have been mapped. A 4.5-kilobase RNA was the major mRNA homologous to the viral DNA sequences between coordinates 0.361 and 0.417 in which mutations in the ICP8 gene have been mapped. Hybridization-selected mRNAs were translated in vitro to determine the primary translation products encoded in each region. The glycoprotein B- and ICP8-specific polypeptides were identified by immunoprecipitation with specific antisera. The translation products encoded by the glycoprotein B gene were 103,000 and 99,000 in molecular weight. The translation products encoded by the ICP8 gene were 125,000 and 122,000 in molecular weight.     

Organization and expression of two tandemly oriented genes encoding ribulosebisphosphate carboxylase/oxygenase activase in barley

We have isolated and structurally characterized genomic DNA and cDNA sequences encoding ribulose-1,5-bisphosphate carboxylase/oxygenase (Rbu-P2 carboxylase) activase from barley (Hordeum vulgare L.). Three Rbu-P2 carboxylase activase (Rca) polypeptides are encoded in the barley genome by two closely linked, tandemly oriented nuclear genes (RcaA and RcaB); cDNAs encoding each of the three Rbu-P2 carboxylase activase polypeptides were isolated from cDNA libraries of barley leaf mRNA. RcaA produces two mRNAs, which encode polypeptides of 42 and 46 kDa, by an alternative splicing mechanism identical to that previously reported for spinach and Arabidopsis Rca genes (Werneke, J.M., Chatfield, J.M., and Ogren, W. L. (1989) Plant Cell 1, 815-825). RcaB is transcribed to produce a single mRNA, which encodes a mature peptide of 42 kDa. Genomic Southern blots indicate that RcaA and RcaB represent the entire Rbu-P2 carboxylase activase gene family in barley. The genes share 80% nucleotide sequence identity, and the 42-kDa polypeptides encoded by RcaA and RcaB share 87% amino acid sequence identity. Coding regions of the two barley Rca genes are separated by 1 kilobase pair of flanking DNA. DNA sequence motifs similar to those thought to control light-regulated gene expression in other nuclear-encoded plastid polypeptide genes are found at the 5' end of both barley Rca genes. Probes specific to three mRNAs were used to determine the relative contribution each species makes to the total Rca mRNA pool.     

Spontaneous deletion of a 20-kilobase DNA segment carrying genes specifying isopropylbenzene metabolism in Pseudomonas putida RE204.

The genes encoding isopropylbenzene metabolism in Pseudomonas putida RE204 are readily lost in two ways: by loss (curing) of plasmid pRE4 which specifies the catabolic pathway and by deletion from pRE4 of an approximately 20-kilobase segment of DNA carrying the catabolic genes. The presence of DNA sequences at the ends of the catabolic gene region sharing homology with one another suggests that the deletions result from recombination events between these homologous sequences.     

Organization and primary sequence of multiple genes coding for the apopolysialoglycoproteins of rainbow trout

We have shown that the mRNAs for apopolysialoglycoproteins (apoPSGP) of rainbow trout contain various numbers of a repetitive sequence of 39 base-pairs encoding mature apoPSGP, and that this sequence is bordered by highly homologous 5' and 3' regions encoding pre-, pro- and telopeptides. These mRNAs are thought to be transcribed from different genes that constitute a large multiple gene family (more than 100 members). Here, we have determined the structures of several members of the apoPSGP gene family. The results show that two of three genomic DNA fragments contain two independent apoPSGP genes in the same orientation with unrelated sequences intervening. Five characterized genes have essentially the same organization and sequence. Each gene has four exons, and CAAT and TATA sequences were found in the 5'-flanking regions. However, two noteworthy differences were observed among the five genes; a diversity in the number of the 39 base-pair repeats, also observed among the cDNA clones, and a one-base polymorphism in the 39 base-pair repeat, which causes an amino acid change. This polymorphism was not detected among the cDNA clones obtained. The boundary positions of the genes are various and contain no transposon-like structures. The variation in the number of repeats and the absence of a rule for bordering positions of the genes suggest that apoPSGP genes may have been amplified by gene duplications, unequal recombination, and selection of chromosomes having larger numbers of apoPSGP genes.     

Sequence analysis and comparison of int and xis genes from staphylococcal bacteriophages L54a and phi 11.

The DNA fragment encoding the integrase and excisionase genes involved in site-specific recombination of staphylococcal bacteriophage phi 11 was cloned and sequenced. The int and xis genes and the recombination site, attP, were highly clustered in a 1.7-kilobase DNA fragment with the gene order attP-int-xis. The int and xis genes were transcribed divergently, with the int gene transcribed toward the attp site and the xis gene transcribed away from the attP site. The deduced Int is a basic protein of 348 residues with an estimated molecular weight of 41,357. In contrast, the deduced Xis is an acidic protein containing 66 amino acids with an estimated molecular weight of 7,621. The site-specific recombination system of phi 11 was compared with that of a closely related bacteriophage, L54a.     

Mouse histocompatibility-related genes are not conserved in other mammals

In addition to the genes for classical H-2 antigens, the H-2 complex of the mouse contains numerous homologous genes belonging to several distinct families. It is not known whether they have any functions. To address this question, I have investigated whether these genes are separately conserved in evolution. Subcloned 5' gene segments, encoding the variable domains, were used as hybridisation probes on genomic DNA blots of various mammals. Only the largest gene family, which includes the classical H-2/HLA genes, is detectable in humans and other mammals. The other gene families, including Qa-2 and T1a, are not conserved even in rodents. Most or all of their coding sequences are therefore redundant.