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PubMed1978

Structural features of normal and complemented forms of the Neurospora isopropylmalate isomerase.

The isopropylmalate isomerase (EC 4.2.1.33) of Neurospora crassa is a globular protein consisting of a single polypeptide chain with a molecular weight of about 90,000. The isomerase cannot easily be freed of a contaminating protease which cleaves the enzyme into two major fragments, one of approximately 56,000 and the other 37,000 daltons. This suggests that the folded polypeptide chain may contain some hinge point or loop exposed on the surface which makes it susceptible to proteolytic attack. Most of the isomerase activity extracted from the wild-type strain is in monomer form. However, a small fraction of the activity in crude extracts is found in multimeric aggregates, and the active isomerase extracted from complementing leu-2 heterokaryons consists entirely of dimers and higher multimers. These observations suggest that, though active as a monomer, a significant fraction of the normal enzyme might be organized in multimeric form within the cell.

Amino Acids↗
PubMed1982

Structural features of the herpes simplex virus alpha gene 4, 0, and 27 promoter-regulatory sequences which confer alpha regulation on chimeric thymidine kinase genes.

Previous studies have shown that herpes simplex virus genes form three groups, alpha, beta, and gamma, whose expression is coordinately regulated and sequentially ordered in a cascade fashion. Chimeric genes constructed by fusion of the coding and 5' nontranslated leader sequences of the thymidine kinase (TK) gene to the sequences upstream from the site of initiation of transcription of alpha genes 4 and 27 are regulated as alpha genes and are induced in cells converted to TK+ phenotype by infection with TK- virus. In alpha gene 4 (S. Mackem and B. Roizman, Proc. Natl. Acad. Sci. U.S.A. 79:4917-4921, 1982), both the promoter and the regulatory region are separable and movable. The promoter permits expression but not induction when fused to TK in the noncoding leader region of the gene. The regulator, when fused to the promoter of an expressible but noninducible portion of the natural beta TK, renders the gene inducible as an alpha gene; it consists of multiple regulatory units acting cumulatively. In this paper, we report on the precise site of initiation of transcription of alpha gene 0 within the inverted b sequences of the L component of viral DNA. We also report the following. (i) The chimeric gene consisting of the coding and 5' nontranslated leader regions of the TK gene fused to portions of the domain of alpha gene 0 extending largely upstream from the site of initiation of transcription of alpha gene 0 was regulated in the same fashion as the alpha 4- and alpha 27-TK chimeras. The regulatory region in the alpha gene 0 is largely upstream from nucleotide - 140. (ii) The promoter-regulatory regions of alpha genes 0, 4, and 27 share TATA sequences, A + T-rich (consensus) sequences occurring in regulating regions of alpha genes 0 and 4 in more than one copy, and multiple G + C-rich inverted repeats. The relation of these sequences to the function of the promoter-regulatory regions of the alpha genes is discussed.

Animals↗
PubMed2007

Distinct structural features of caprin-1 mediate its interaction with G3BP-1 and its induction of phosphorylation of eukaryotic translation initiation factor 2alpha, entry to cytoplasmic stress granules, and selective interaction with a subset of mRNAs.

Caprin-1 is a ubiquitously expressed, well-conserved cytoplasmic phosphoprotein that is needed for normal progression through the G(1)-S phase of the cell cycle and occurs in postsynaptic granules in dendrites of neurons. We demonstrate that Caprin-1 colocalizes with RasGAP SH3 domain binding protein-1 (G3BP-1) in cytoplasmic RNA granules associated with microtubules and concentrated in the leading and trailing edge of migrating cells. Caprin-1 exhibits a highly conserved motif, F(M/I/L)Q(D/E)Sx(I/L)D that binds to the NTF-2-like domain of G3BP-1. The carboxy-terminal region of Caprin-1 selectively bound mRNA for c-Myc or cyclin D2, this binding being diminished by mutation of the three RGG motifs and abolished by deletion of the RGG-rich region. Overexpression of Caprin-1 induced phosphorylation of eukaryotic translation initiation factor 2alpha (eIF-2alpha) through a mechanism that depended on its ability to bind mRNA, resulting in global inhibition of protein synthesis. However, cells lacking Caprin-1 exhibited no changes in global rates of protein synthesis, suggesting that physiologically, the effects of Caprin-1 on translation were limited to restricted subsets of mRNAs. Overexpression of Caprin-1 induced the formation of cytoplasmic stress granules (SG). Its ability to bind RNA was required to induce SG formation but not necessarily its ability to enter SG. The ability of Caprin-1 or G3BP-1 to induce SG formation or enter them did not depend on their association with each other. The Caprin-1/G3BP-1 complex is likely to regulate the transport and translation of mRNAs of proteins involved with synaptic plasticity in neurons and cellular proliferation and migration in multiple cell types.

Amino Acid Motifs↗
PubMed1987

c-mos proto-oncogene RNA transcripts in mouse tissues: structural features, developmental regulation, and localization in specific cell types.

c-mos RNA transcripts have been previously detected in mouse gonadal tissue and in late-term embryos. Here, we show that they are also present at low levels in placenta and in adult mouse brain, kidney, mammary gland, and epididymis. Marked differences are observed in the size of the mos RNA transcripts detected in different tissues. All transcripts appear to end at the same 3' position, and the tissue-specific size variations appear to be due to the use of different promoters. For example, the testicular and ovarian RNA transcripts initiate approximately 280 and approximately 70 base pairs, respectively, upstream from the first initiation codon, but both end at a common site downstream from the mos open reading frame. The expression of mos is developmentally regulated in gonadal tissue. Thus, the level of mos transcripts in testes is low for the first 3 weeks after birth, increases at least 10-fold around day 25, and reaches adult levels by day 30. In contrast, ovaries from preweaning mice contain a higher level of mos mRNA compared to ovaries from adult mice. In cell fractionation experiments we show that mos transcripts are present in haploid germ cells. We find that these transcripts are associated with monosomes and polysomes. The peculiar pattern of mos expression in mouse gonadal tissue suggests a role for the c-mos proto-oncogene in germ cell differentiation.

Age Factors↗
PubMed1989

UbiA, the major polyubiquitin locus in Caenorhabditis elegans, has unusual structural features and is constitutively expressed.

Ubiquitin is a multifunctional 76-amino-acid protein which plays critical roles in many aspects of cellular metabolism. In Caenorhabditis elegans, the major source of ubiquitin RNA is the polyubiquitin locus, UbiA. UbiA is transcribed as a polycistronic mRNA which contains 11 tandem repeats of ubiquitin sequence and possesses a 2-amino-acid carboxy-terminal extension on the final repeat. The UbiA locus possesses several unusual features not seen in the ubiquitin genes of other organisms studied to date. Mature UbiA mRNA acquires a 22-nucleotide leader sequence via a trans-splicing reaction involving a 100-nucleotide splice leader RNA derived from a different chromosome. UbiA is also unique among known polyubiquitin genes in containing four cis-spliced introns within its coding sequence. Thus, UbiA is one of a small class of genes found in higher eucaryotes whose heterogeneous nuclear RNA undergoes both cis and trans splicing. The putative promoter region of UbiA contains a number of potential regulatory elements: (i) a cytosine-rich block, (ii) two sequences resembling the heat shock regulatory element, and (iii) a palindromic sequence with homology to the DNA-binding site of the mammalian steroid hormone receptor. The expression of the UbiA gene has been studied under various heat shock conditions and has been monitored during larval moulting and throughout the major stages of development. These studies indicate that the expression of the UbiA gene is not inducible by acute or chronic heat shock and does not appear to be under nutritional or developmental regulation in C. elegans.

Animals↗
PubMed1976

Some chemical and structural features of the conidial wall of Trichoderma viride.

Cell wall of spores of Trichoderma viride contains polymers similar to those of mycelial cell wall, such as beta-(1 leads to 3), beta-(1 leads to 6) glucans and protein, but chitin, always present in the mycelium, cannot be found in spores. Melanin, which in other fungi appears associated with chitin, replaces this polymer in the spore wall of T. viride and is located in the outermost layer. Attempts to characterize the pigment of the spore wall indicate that it is a non-indolic melanin-like polyphenol.

Cell Wall↗
PubMedDate not supplied

Dynamic and structural features of a case of compulsive neurosis as revealed in dreams.

Several examples of the manifest dreams reported by a patient with a compulsive neurosis are presented. An outstanding feature of the dreams was the sudden shift of the dreamer's self-representation from the role of criminal to the role of policeman. This shift is thought to parallel the oscillation between unconscious instinctual gratification and conscious attempts at reparation which is the main dynamic feature of the compulsive neurosis in waking life. The shift of orientation of the self reflects the operation of early defense mechanisms against the sadistic impulse. It also portrays graphically an early stage in the internalization process which leads ultimately to the creation of the superego. The repetitive nature of the dreams indicated that the patient had become fixated at this particular point in the course of his psychic development. It is interesting to note that like the Rat Man this patient suffered from a chronically undescended testicle. The real defect in the sexual apparatus in both patients may have been a factor which favored regression of the libido from the genital stage to the anal-sadistic stage.

Adult↗
PubMed1991

Structural features of the core proteins of human airway mucins ascertained by cDNA cloning.

Tracheobronchial secretions are one of the most important elements of the mucociliary system that protects the respiratory mucosa. They contain bronchial mucus, which is composed of a group of macromolecules secreted by the goblet cells of the epithelium and the submucosal glands. Bronchial mucins are the most characteristic molecules of this mucus. They form a group of complex, polydispersed O-linked glycoproteins containing sugars, which make up 80% of their weight. The protein core of human airway mucin has been difficult to sequence by traditional technologies because of its high content of serine and threonine residues linked to numerous oligosaccharide chains. We therefore prepared a lambda gt11 cDNA library from one sample of human tracheobronchial mucosa and screened this library with a polyclonal antibody directed against the apopeptides of human bronchial mucins. We obtained 20 positive clones that were sequenced. These sequences were classified into three different types. The use of the nucleotide probes from these clones in Northern blot analysis showed that the RNA messages were extremely polydispersed. At the current time, four of these probes allow us to map human tracheobronchial mucins genes to at least three different chromosomes. These results suggest that the peptide moiety of the human airway mucin is very heterogeneous.

Bronchi↗
PubMedDate not supplied

Comparative analysis on the structural features of the 5' flanking region of kappa-casein genes from six different species.

Kappa-casein plays an essential role in the formation, stabilisation and aggregation of milk micelles. Control of kappa-casein expression reflects this essential role, although an understanding of the mechanisms involved lags behind that of the other milk protein genes. We determined the 5'-flanking sequences for the murine, rabbit and human kappa-casein genes and compared them to the published ruminant sequences. The most conserved region was not the proximal promoter region but an approximately 400 bp long region centred 800 bp upstream of the TATA box. This region contained two highly conserved MGF/STAT5 sites with common spacing relative to each other. In this region, six conserved short stretches of similarity were also found which did not correspond to known transcription factor consensus sites. On the contrary to ruminant and human 5' regulatory sequences, the rabbit and murine 5'-flanking regions did not harbour any kind of repetitive elements. We generated a phylogenetic tree of the six species based on multiple alignment of the kappa-casein sequences. This study identified conserved candidate transcriptional regulatory elements within the kappa-casein gene promoter.

5' Flanking Region↗
PubMed1989

Hamster placental lactogen-II contains a structural feature unique among the growth hormone-prolactin-placental lactogen family.

Sequence analysis of cDNA for hamster placental lactogen-II (PL-II) revealed that while this protein has a high degree of sequence homology to mouse and rat PL-II it contains a pair of cysteine residues not present in the mouse and rat proteins or in any other known member of the GH-PRL-PL protein family. This unique pair of cysteine residues may be responsible for the extreme tendency of hamster PL-II, compared to other members of the GH-PRL-PL family, to form disulfide-bonded hormone-serum protein complexes.

Amino Acid Sequence↗