Biomedical subjects

Y K Kwon

Publications and source records attributed to Y K Kwon.

28 records · Page 2Linked to original sources

PubMed1996

In postmeiotic male germ cells poly (A) shortening accompanies translation of mRNA encoding gamma enteric actin but not cytoplasmic beta and gamma actin mRNAs.

In the mammalian testis the cytoplasmic beta and gamma actins are expressed in all stages of germ-cell differentiation, whereas gamma enteric actin is expressed in germ cells solely in postmeiotic stages. Northern blot analysis of mouse testicular RNAs reveals actin mRNAs of about 2.1, 1.5, and 1.4 kB. The 2.1-kB mRNAs encode the cytoplasmic beta and gamma actins, whereas the two faster-migrating actin mRNAs encode gamma enteric actin. When postmitochondrial mouse testis extracts are fractionated by sucrose gradient centrifugation, the 1.5-kB gamma enteric actin mRNA is primarily found in the nonpolysomal fraction, whereas the 1.4-kB gamma enteric actin is polysomal. When the poly (A) tails are removed, the nonpolysomal and polysomal gamma enteric actin mRNAs both migrate at 1.3 kB, indicating that the difference in electrophoretic mobilities of the two gamma enteric actin mRNAs is caused by poly (A) length differences. The nonpolysomal and polysomal forms of the cytoplasmic beta and gamma actins show similar electrophoretic mobilities before and after deadenylation. Sequence comparison of the 3' untranslated region of the mouse gamma enteric actin to the 3' untranslated regions of other testicular mRNAs that undergo partial deadenylation reveals three highly-conserved sequence elements. These data demonstrate that the poly (A) shortening of polysomal mRNAs previously seen only with testis-specific mRNAs that are stored as mRNPs also occurs with mRNAs of widely-expressed genes that are expressed in postmeiotic male germ cells. The mRNAs all contain specific conserved sequence elements in their 3' untranslated regions.

Actins↗

PubMed1994

Expression of the neurotrophin receptor TrkC is linked to a favorable outcome in medulloblastoma.

Medulloblastoma, the most common malignant brain tumor of childhood, has a variable prognosis. Although half of the children and young adults with the disease survive longer than 10 years after diagnosis, the others relapse and die despite identical therapy. We have examined the expression of neurotrophins and their receptors in medulloblastoma samples snap frozen in the operating room to preserve RNA integrity. All tumors (n = 12) were found to express mRNA encoding neurotrophin 3 and its receptor TrkC. The level of trkC expression was highly variable, with a more than 50-fold difference between the highest and lowest values. By Kaplan-Meier analysis, patients with tumors expressing high levels of trkC mRNA had significantly longer intervals without disease progression than those with low levels (log-rank, P = 0.03) and a more favorable overall survival (log-rank, P = 0.05). Thus, trkC expression is a prognostic indicator for patients with medulloblastoma.

Brain-Derived Neurotrophic Factor↗

PubMed1993

Proteins homologous to the Xenopus germ cell-specific RNA-binding proteins p54/p56 are temporally expressed in mouse male germ cells.

Antibodies specific for the Xenopus oocyte cytoplasmic 6S mRNA-binding particle p54/p56 and antibodies against Xenopus germ cell DNA-binding protein FRG Y2 recognize two RNA-binding proteins of the mouse testis. The mouse testis proteins, estimated by SDS-PAGE to be about 48 and 52 kDa, form RNA-protein complexes with either translationally regulated or control RNAs, suggesting that they are sequence-independent RNA-binding proteins. The binding of the 48/52-kDa proteins to RNA is reduced by heparin. The expression of the 48/52-kDa mouse proteins is germ cell-specific and developmentally regulated in the testis with a maximal amount of the two proteins being detected in early postmeiotic cells (round spermatids), a cell type where many mRNAs are stored. The 48/52-kDa proteins are detected solely in the nonpolysomal fractions of postmitochondrial adult testis extracts and are not detected in extracts of brain, liver, or prepuberal testes from 12-day-old mice. We conclude that two RNA-binding proteins that appear to be immunological and functional homologues of the Xenopus germ cell-specific RNA/DNA-binding proteins p54/p56/FRG Y2 are present in male germ cells and form complexes with stored mRNAs.

Animals↗

PubMed1993

Binding of a phosphoprotein to the 3' untranslated region of the mouse protamine 2 mRNA temporally represses its translation.

The synthesis of the protamines, the predominant nuclear proteins of mammalian spermatozoa, is regulated during germ cell development by mRNA storage for about 7 days in the cytoplasm of differentiating spermatids. Two highly conserved sequences, the Y and H elements present in the 3' untranslated regions (UTRs) of all known mammalian protamine mRNAs, form RNA-protein complexes and specifically bind a protein of 18 kDa. Here, we show that translation of fusion mRNAs was markedly repressed in reticulocyte lysates supplemented with a mouse testis extract enriched for the 18-kDa protein when the mRNAs contained the 3' UTR of mouse protamine 2 (mP2) or the Y and H elements of mP2. No significant decrease was seen when the fusion mRNAs contained the 3' UTR of human growth hormone. The 18-kDa protein is developmentally regulated in male germ cells, requires phosphorylation for RNA binding, and is found in the ribonucleoprotein particle fractions of a testicular postmitochondrial supernatant. We propose that a phosphorylated 18-kDa protein plays a primary role in repressing translation of mP2 mRNA by interaction with the highly conserved Y and H elements. At a later stage of male gamete differentiation, the 18-kDa protein no longer binds to the mRNA, likely as a result of dephosphorylation, enabling the protamine mRNA to be translated.

Animals↗

PubMed1991

Cytoplasmic protein binding to highly conserved sequences in the 3' untranslated region of mouse protamine 2 mRNA, a translationally regulated transcript of male germ cells.

The expression of the protamines, the predominant nuclear proteins of mammalian spermatozoa, is regulated translationally during male germ-cell development. The 3' untranslated region (UTR) of protamine 1 mRNA has been reported to control its time of translation. To understand the mechanisms controlling translation of the protamine mRNAs, we have sought to identify cis elements of the 3' UTR of protamine 2 mRNA that are recognized by cytoplasmic factors. From gel retardation assays, two sequence elements are shown to form specific RNA-protein complexes. Protein binding sites of the two complexes were determined by RNase T1 mapping, by blocking the putative binding sites with antisense oligonucleotides, and by competition assays. The sequences of these elements, located between nucleotides + 537 and + 572 in protamine 2 mRNA, are highly conserved among postmeiotic translationally regulated nuclear proteins of the mammalian testis. Two closely linked protein binding sites were detected. UV-crosslinking studies revealed that a protein of about 18 kDa binds to one of the conserved sequences. These data demonstrate specific protein binding to a highly conserved 3' UTR of translationally regulated testicular mRNA.

Animals↗

PubMed1991

junD mRNA expression differs from c-jun and junB mRNA expression during male germinal cell differentiation.

The members of the jun family of protooncogenes (junB, c-jun, and junD) share a high degree of sequence homology and function as transcriptional regulators. Here we compare the pattern of junD mRNA expression during spermatogenesis to that of junB and c-jun (Alcivar et al.: J Biol Chem 265:20160-20165, 1990). junD transcripts are present at high levels in total RNA obtained from both prepuberal and adult intact testes, with the highest levels at stages containing predominantly premeiotic and postmeiotic germ cells. Analyses of cells isolated from testes of 8-day-old mice indicate that the level of the 1.8 kb junD mRNA is higher in type B spermatogonia than in type A spermatogonia. In testes of 17-day-old mice, the highest junD mRNA levels are detected in preleptotene spermatocytes compared to leptotene/zygotene and prepuberal pachytene spermatocytes. In cells from adult testes, the junD mRNA levels are higher in postmeiotic round spermatids and residual bodies/cytoplasts than in meiotic pachytene spermatocytes. An additional junD transcript of about 1.6 kb is detected in postmeiotic cells. Analyses of polysomal and nonpolysomal RNAs prepared from isolated testicular cells indicate that in early meiotic cell types the junD transcript is more efficiently loaded onto polysomes than in later cell types. In summary, the pattern of expression of junD differs from that of junB and c-jun during spermatogenesis most notably in that 1) junD mRNA levels do not increase following dissociation of testicular cells and 2) in contrast to the nearly undetectable levels of junB and c-jun mRNAs in adult postmeiotic testicular cells, high levels of junD mRNAs are seen.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

The mouse transition protein 1 gene contains a B1 repetitive element and is located on chromosome 1.

The gene for mouse transition protein 1 (mTP1) was isolated, sequenced, and chromosomally mapped. The nucleotide sequence of 1895 bp of a 6.4-kb mTP1 genomic subclone was determined to include 788 bp of 5' flanking region, 564 bp of coding region including a 396-bp intron and a TAA stop codon, and 543 bp of 3' flanking region. The mTP1 gene contains a B1 repeat sequence within the only intron of the gene. The transcriptional start site of the mTP1 mRNA was determined to be located 31 bases upstream of the ATG translational start codon. Southern blot analysis demonstrated the presence of sequences homologous to the mTP1 cDNA in the genomes of the rat, hamster, bull, boar, dog, horse, ram, human, and two marsupials (the American opossum and Monodelphis), suggesting that the mTP1 gene sequence is widely conserved. The TP1 gene has been mapped by analysis of restriction fragment length variants (RFLV) in an interspecific backcross to a position 0.7 +/- 0.4 cM telomeric of Mylf and 1.2 +/- 0.5 cM centromeric of Vil on mouse chromosome 1.

Amino Acid Sequence↗

PubMed1991

Cytoplasmic localization during storage and translation of the mRNAs of transition protein 1 and protamine 1, two translationally regulated transcripts of the mammalian testis.

During spermatogenesis in mammals, the transcripts of transition protein 1 (TP 1) and protamine 1 (Prm 1) are under translational regulation. Following their transcription in round spermatids, the mRNAs for TP 1 and Prm 1 are stored in the cytoplasm from 3-7 days before being translated towards the end of spermatogenesis. To test the hypothesis that the inactivation or activation of transcripts during spermiogenesis could be mediated by mRNA compartmentalization in the cytoplasm of spermatids, light and electron microscopy were used to localize, by in situ hybridization, the cellular and subcellular sites of stored and translated mRNAs for these two testis-specific transcripts. During early spermiogenesis (before step 7) nuclear transcripts of both TP 1 and Prm 1 were seen. After step 7 the TP 1 and Prm 1 mRNAs were only detected in the cytoplasm. Throughout spermiogenesis the cytoplasmic mRNAs were not localized to any membrane-bound organelles such as the endoplasmic reticulum or mitochondria or to non-membrane-bound structures such as the chromatoid body. These studies demonstrate that the translational arrest of the TP 1 and Prm 1 mRNAs is not primarily controlled by compartmentalized storage in the cytoplasm of spermatids. Moreover, when translation of these mRNAs occurs in elongated spermatids, the mRNAs are present throughout the cytoplasm.

Animals↗

PubMed1990

The mouse smooth muscle gamma actin gene is on chromosome 6.

Smooth muscle gamma actin (Actg) is expressed in smooth muscle and in haploid male germ cells. In order to further characterize the Actg gene, a 60-nucleotide-long isotype-specific probe was synthesized. Single bands of DNA were detected when this oligonucleotide was used to probe blots of mouse genomic DNA digested with PstI, EcoRI, KpnI, or XbaI. These results suggest Actg is a single-copy gene with no detectable pseudogenes. The Actg gene was mapped to mouse chromosome 6 by Southern blot analysis of DNA isolated from 15 mouse-hamster hybrid cell lines.

Actins↗

PubMedDate not supplied

Outbreak of Fowl cholera in Baikal teals in Korea.

Fowl cholera (FC) caused by Pasteurella multocida was diagnosed in waterfowl, Baikal teals (Anas formosa), submitted to the National Veterinary Research and Quarantine in Korea. The total number of mortalities was 13,228 out of approximately 100,000 birds that wintered in Cheonsoo Bay, the most important habitat area of Baikal teals in the world. Clinical signs were detected in only a few birds because of sudden death. Grossly, the dead Baikal teals had lesions consistent with FC, including multifocal necrotic foci in the liver with enlargement, petechial or ecchymotic hemorrhages on the heart, and mucoid exudates in the duodenal mucosa. Microscopically, there were hepatocytic necrosis with bacterial colonization, hemorrhage and necrosis in the myocardium, and hemorrhagic enteritis. Pasteurella multocida was isolated from the liver and the heart of all birds examined, and the isolate (P-627) was the serotype 1 X 12 X 13 by the agar gel immunodiffusion test. In order to estimate the virulence of P-627, 5-wk-old commercial ducks were exposed intramuscularly or intratracheally to the bacterium. On the basis of mortality rate, the isolate, P-627, was found to be highly virulent. This is the first report of an outbreak of FC in Baikal teals in Korea.

Animals↗