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Biomedical subjects

T Jahnsen

Publications and source records attributed to T Jahnsen.

At least 37 records · Page 2Linked to original sources
PubMed1997

The human gene for the regulatory subunit RI alpha of cyclic adenosine 3', 5'-monophosphate-dependent protein kinase: two distinct promoters provide differential regulation of alternately spliced messenger ribonucleic acids.

The present study reports the exon-intron organization of the human RI alpha gene of cAMP-dependent protein kinase and approximately kilobases (kb) of the 5'-flanking region obtained by isolation and sequencing of several phage clones from human genomic libraries. The RI alpha gene is composed of nine coding exons of varying lengths, separated by introns, giving the gene a total length of at least 21 kb. our recent cloning of a processed RI alpha pseudogene with a 5'-noncoding region different from the previously reported RI alpha complementary RNA indicated that the RI alpha gene may have multiple leader exons giving rise to alternately spliced messenger RNAs (mRNAs). Reverse transcription of human testis RNA followed by PCR identified two different RI alpha mRNA species (RI alpha 1a and RI alpha 1b) containing distinct sequences due to alternately splicing the gene. The previously known RI alpha 1b mRNA revealed low constitutive expression in a human B lymphoid cell line (Reh) and was stimulated only 4- to 6-fold by treatment with cAMP. In contrast, very low levels of the novel RI alpha 1a mRNA were present in untreated Reh cells, but were stimulated 40-to 50-fold by cAMP. The 5'-flanking sequence of the RI alpha gene was G/C rich and did not contain any TATA box. Several putative transcription initiation sites were identified in front of each leader exon (exons 1a and 1b) by the 5'-rapid amplification of complementary DNA ends technique. To determine whether the sequences 5' of both leader exons had promoter activities, the 5'-flanking sequences of exons 1a and 1b were inserted in front of a chloramphenicol acetyltransferase reporter gene, and their ability to direct transcription were examined. Transfection of these constructs into rat GH4C1 cells demonstrated that both constructs had promoter activities, as evidenced by high levels of chloramphenicol acetyltransferase activity.

Aged↗
PubMed1996

The gene encoding the catalytic subunit C alpha of cAMP-dependent protein kinase (locus PRKACA) localizes to human chromosome region 19p13.1.

We have determined the chromosomal localization of the gene for the catalytic subunit C alpha of cAMP-dependent protein kinase (locus PRKACA) to human chromosome 19 using polymerase chain reaction (PCR) and Southern blot analysis of two different somatic cell hybrid mapping panels. In addition, PCR analysis of a chromosome 19 mapping panel revealed the presence of a human C alpha-specific amplification product only in cell lines containing the region 19p13.1 to 19q12. Finally, two-color fluorescence in situ hybridization to metaphase chromosomes using the human C alpha cDNA and human chromosome 19 inter-Alu-PCR product as probes localized the human C alpha gene to chromosome region 19p13.1.

Animals↗
PubMed1996

Fast and slow cyclic nucleotide-dissociation sites in cAMP-dependent protein kinase are transposed in type Ibeta cGMP-dependent protein kinase.

Both cyclic GMP-dependent protein kinase (cGK) and cyclic AMP-dependent protein kinase (cAK) contain two distinct cyclic nucleotide-binding sites referred to as fast and slow sites based on cyclic nucleotide dissociation behavior. In cAK, the fast site lies amino-terminal to the slow site, and sequence homologies between cAK and cGK have suggested similar positioning for the sites in cGK. Recombinant human type Ibeta cGK (wild type (WT) cGK) was overexpressed, and the properties of purified WT cGK and native type Ibeta cGK were similar. cGK was mutated singly at Thr-193 (T193A, T193V, and T193S) and Thr-317 (T317A, T317V, and T317S), which have been predicted to provide cGMP specificity in the cGMP-binding sites of cGK; a double mutant (T193A/T317A) was produced also. Compared with WT cGK, half-maximal activation (Ka) of mutant cGKs by cGMP was increased 2- (T317A), 27- (T193A), or 63-fold (T193A/T317A), but the Ka for cAMP of these mutants was essentially unchanged. The T193A and T193V mutants had a large increase in the rate of the slow component of [3H]cGMP dissociation, but in the T317A and T317V mutants, there was no change in the slow component. The T193S and T317S mutants had only minor effects on [3H]cGMP dissociation, thus establishing the importance of the hydroxyl group of Thr-193 and -317 for cGMP binding to cGK. Thus, in type Ibeta cGK, the slow cGMP-binding site is identified as the amino-terminal site in contrast to the order assigned to the fast and slow cAMP-binding sites of cAK.

Amino Acid Sequence↗
PubMed1996

Molecular cloning, cDNA structure, and chromosomal localization of the human type II cGMP-dependent protein kinase.

The type II cGMP-dependent protein kinase is an enzyme originally isolated from the small intestine, and is thought to be involved in the regulation of intestinal ion transport and fluid secretion. A complementary DNA clone encoding a part of the human type II cGMP-dependent protein kinase was isolated from a cerebellum library. Based on sequence information from this complementary DNA, the 5'-end of the type II cGMP-dependent protein kinase was amplified from human brain messenger RNA using polymerase chain reaction. The composite complementary DNA encoded a 762 amino acid protein with a calculated molecular mass of 87.4 kDa. Messenger RNAs encoding the type II cGMP-dependent protein kinase were detected in small intestine, colon and prostate. By using polymerase chain reaction and Southern blotting on somatic cell hybrids, the gene encoding, the type II cGMP-dependent protein kinase was mapped to human chromosome 4q13.1-q21.1.

Amino Acid Sequence↗
PubMed1994

Characterization of in-vitro-translated human regulatory and catalytic subunits of cAMP-dependent protein kinases.

Full-length human cDNAs for all the different regulatory (R) and catalytic (C) subunits of cAMP-dependent protein kinases (PKA) were transcribed and translated in a cell-free in vitro system. The resulting proteins were characterized with respect to molecular size, isoelectric focusing, immunoreactivity, cAMP binding, and to what extent the RII protein subunits revealed mobility shifts upon phosphorylation by catalytic subunit of PKA. We were able to express cDNAs for all the human R (RI alpha, RI beta, RII alpha and RII beta) and C (C alpha, C beta and C gamma) subunits in a wheat-germ extract. [35S]Methionine-labelled in-vitro-translated products were analyzed by SDS/PAGE and revealed distinct protein bands with apparent molecular masses of 49 (RI alpha), 54-55 (RI beta), 51 (RII alpha) and 53 kDa (RII beta) for the R subunits. In vitro transcription/translation of the cDNAs for the C subunits of PKA gave proteins with molecular masses of approximately 40 kDa for all the different C subunits. Phosphorylation of RII alpha and RII beta by the C subunit of PKA, revealed a distinct mobility shift of the RII alpha subunit on one-dimensional SDS/PAGE (51-54 kDa), but not of RII beta (53 kDa). Further characterization of the R subunits by two-dimensional SDS/PAGE revealed that RI alpha was more acidic than RI beta, with pIs of 6.1-6.0 and 6.4-6.2, respectively. Furthermore, the RII alpha protein was more basic than RII beta, with pIs of approximately 5.4-5.3 and 5.3-5.1, respectively. All the in-vitro-translated R subunits could be photoaffinity labelled by the cAMP-analog 8-azido-[32P]cAMP and were also detected by immunoprecipitation with subunit-specific antibodies.

Affinity Labels↗
PubMed1994

Location of cAMP-dependent protein kinase type I with the TCR-CD3 complex.

Selective activation of cyclic adenosine 3',5'-monophosphate (cAMP)-dependent protein kinase type I (cAKI), but not type II, is sufficient to mediate inhibition of T cell replication induced through the antigen-specific T cell receptor-CD3 (TCR-CD3) complex. Immunocytochemistry and immunoprecipitation studies of the molecular mechanism by which cAKI inhibits TCR-CD3-dependent T cell replication demonstrated that regulatory subunit I alpha, along with its associated kinase activity, translocated to and interacted with the TCR-CD3 complex during T cell activation and capping. Regulatory subunit II alpha did not. When stimulated by cAMP, the cAKI localized to the TCR-CD3 complex may release kinase activity that, through phosphorylation, might uncouple the TCR-CD3 complex from intracellular signaling systems.

Carrier Proteins↗
PubMed1994

Human regulatory subunit RI beta of cAMP-dependent protein kinases: expression, holoenzyme formation and microinjection into living cells.

The human regulatory subunit RI beta of cAMP-dependent protein kinases was expressed in Escherichia coli as a fusion protein with glutathione S-transferase. Purification was performed by affinity chromatography on glutathione-agarose beads after cleavage with thrombin. The human recombinant RI beta protein migrated at 55 kDa on SDS-PAGE and displayed immunoreactivity with an anti-human RI beta antiserum. Furthermore, the purified recombinant RI beta protein was shown to exist as a dimer that was able to form holoenzyme with the catalytic subunit C alpha. The rate of RI beta 2C alpha 2 holoenzyme formation was faster in the presence than in the absence of MgATP. The kinase activity measured before and after adding cAMP to the holoenzyme showed that the presence of cAMP resulted in holoenzyme dissociation and release of active C alpha-subunit, due to cAMP binding to RI beta. Compared to a RI alpha 2C alpha 2 holoenzyme, the RI beta 2C alpha 2 holoenzyme exhibited a more than twofold higher sensitivity to cAMP. The subcellular localization of RI beta was analyzed in quiescent REF-52 fibroblasts and Wistar rat thyroid (WRT) cells after microinjection of fluorescently labeled proteins into the cytoplasm. A cytoplasmic distribution was observed when free RI beta was injected, whereas free C alpha injected into the cytoplasm appeared in the nucleus. When holoenzymes with labeled RI beta and unlabeled C alpha, or unlabeled RI beta and labeled C alpha, were injected, unstimulated cells showed fluorescence in the cytoplasm of both cell types. REF-52 cells stimulated with 8-bromo-cAMP (8-Br-cAMP) and WRT cells treated with thyrotropin (TSH) showed fluorescence mainly in the cytoplasm when RI beta was the labeled subunit of the in vivo dissociated holoenzyme. In contrast, nuclear fluorescence was evident from the release and translocation of labeled C alpha from the holoenzyme complex after stimulation with 8-Br-cAMP or TSH.

Allosteric Regulation↗
PubMed1994

Cyclic AMP sensitive signalling by the CD28 marker requires concomitant stimulation by the T-cell antigen receptor (TCR/CD3) complex.

We have previously demonstrated that activation of cAMP-dependent protein kinase (cAK) type I (cAKI, RI alpha 2-C beta 2) mediates the inhibitory effects of cAMP on T-cell replication induced through the TCR/CD3 complex. In the present study we have investigated the effect of cAMP on T-cell DNA synthesis, tyrosine phosphorylation of a 100 kDa protein (pp100) and IL2 mRNA expression, induced through stimulation of the TCR/CD3- and/or the CD28 molecules. Our results demonstrate that tyrosine phosphorylation of pp100 stimulated by anti-CD3 is inhibited by cAMP both in the presence and absence of the phorbol ester PMA, and reflects the changes seen in IL2 mRNA expression and T-cell replication. Combined stimulation with anti-CD3 and anti-CD28, which gives a synergistic response in T-cell replication, gave pp100 phosphorylation and IL2 mRNA expression sensitive to cAMP-dependent inhibition. When PMA was added in addition to anti-CD3 and anti-CD28, the inhibitory effect of cAMP on both T-cell replication and pp100 phosphorylation was completely abolished. The fact that pp100 phosphorylation in response to TCR/CD3-, CD28- and PMA stimulation and cAMP mediated inhibition are identical to the effects of the same stimuli on T-cell proliferation, makes this protein an interesting candidate in downstream signalling from these receptors. In addition, our results are compatible with a model where cAMP, through activation of cAKI, eliminates both the PTK and PKC activating capability of the T-cell receptor at a site(s) proximal to PKC activation. Furthermore, the CD28 molecule which activates PTKs, enters the PTK cascade at a point distal to the target(s) for cAKI action. Therefore, during CD28 signalling PKC activation can be achieved either by TCR/CD3 stimulation (inhibited by cAMP), or directly by PMA (not inhibited by cAMP).

CD28 Antigens↗
PubMed1994

Regulation of growth in a neoplastic B cell line by transfected subunits of 3',5'-cyclic adenosine monophosphate-dependent protein kinase.

cAMP inhibits the proliferation of both normal peripheral blood B and T lymphocytes as well as the proliferation of a human neoplastic B precursor cell line (Reh). To positively show that this is mediated via the the catalytic subunit, C alpha, of cAMP-dependent protein kinase, stably transfected Reh cell lines overexpressing C alpha were established. This was achieved by transfection with a construct confering hygromycin resistance together with a zinc-inducible expression of C alpha from the human metallothionine promoter. C alpha transfected clones were shown to confer a 2- to 2.5-fold zinc-dependent increase in C alpha messenger RNA, immunoreactive C, and phosphotransferase activity. The growth rate of clones transfected with C alpha was retarded, and a zinc-dependent inhibition of cell proliferation was demonstrated in the presence of a small trigger dose of forskolin. In contrast, overexpression of the regulatory subunit I alpha had no effect on cAMP-dependent inhibition of cell proliferation. Furthermore, expression of mutant regulatory subunit I alpha AB, which renders cAMP-dependent protein kinase unresponsive to cAMP, clearly protected against that inhibitory effect of cAMP. These data provides evidence that activation of the C subunit (C alpha) of cAMP-dependent protein kinase mediates the inhibitory action of cAMP on cell proliferation in Reh cells.

B-Lymphocytes↗
PubMed1994

Human cyclic GMP-dependent protein kinase I beta overexpression increases phosphorylation of an endogenous focal contact-associated vasodilator-stimulated phosphoprotein without altering the thrombin-evoked calcium response.

The role of the cGMP-dependent protein kinase (cGK) and one of its major substrates, the vasodilator-stimulated phosphoprotein (VASP), in the regulation of a receptor-evoked calcium response was investigated. The human type I beta cGK was stably transfected in human embryonic kidney 293 cells and Swiss mouse 3T6 fibroblasts, which contained significant or no detectable levels of the focal adhesion protein VASP, respectively. Western blot analysis and protein kinase activity measurements demonstrated an 8-fold overexpression of cGK-I beta in 293 cells (7-fold in 3T6 cells), representing an intracellular cGK concentration of 0.33 microM. In experiments with intact 293 cells expressing cGK-I beta, beta-phenyl-1,N2-etheno-cGMP and 8-(p-chlorophenylthio)-cGMP were capable of converting up to 30-40% of the 46-kDa VASP to its 50-kDa phospho- form, equivalent to results observed with cGMP analogs that cause a marked inhibition of the stimulated Ca2+ transient in intact human platelets. In contrast to platelets, preincubation of fura-2-loaded 293 and 3T6 cells with 8-(p-chlorophenylthio)-cGMP did not significantly inhibit thrombin-evoked calcium transients, although sufficient cGK-mediated VASP phosphorylation was clearly detectable under these conditions in cGK-I beta-expressing 293 cells. These results demonstrate that cGK inhibition of agonist-evoked calcium mobilization is not a mechanism common to all cell types and that VASP phosphorylation may not be an essential or sufficient component of the cGK effect on calcium levels. In contrast, the observed VASP phosphorylation mediated by recombinant human cGK-I beta in intact 293 cells does support the hypothesis that focal adhesions and their associated proteins are important cellular sites of cGK action.

Blood Proteins↗
PubMed1993

Reciprocal regulation of mRNA and protein for subunits of cAMP-dependent protein kinase (RI alpha and C alpha) by cAMP in a neoplastic B cell line (Reh).

The present study examines the activity, levels of expression and regulation of cAMP-dependent protein kinase subunits during cAMP-mediated inhibition of Reh cell proliferation. Human Reh cells express mRNAs for the RI alpha and C alpha subunits of cAK at high levels and are practically devoid of cAMP-dependent protein kinase type II. Treatment with isoproterenol, forskolin, or a cAMP analog increased RI alpha mRNA in a time- and concentration-dependent manner (maximal, 4-fold, at 4-8 h). Messenger RNA for C alpha was also stimulated by cAMP, although with slower kinetics (maximal, 2-fold, at 16-24 h). Nuclear run-on assays showed a 2-fold increase in RI alpha gene transcription, whereas that of C alpha was unchanged. In spite of the stimulatory effects of cAMP on mRNAs for both RI alpha and C alpha, phosphotransferase activity and specific [3H]cAMP binding decreased rapidly after treatment with either cAMP or forskolin. Interestingly, the decrease in R and C activity preceded the increase in RI alpha and C alpha mRNA levels, raising the question whether increased mRNA levels may be secondary to the decrease in RI alpha or C alpha protein. The finding that the protein synthesis inhibitor cycloheximide gave changes in RI alpha and C alpha mRNA similar to cAMP and that co-treatment with cycloheximide and cAMP resulted in additive effects tend to support this notion.

Adenylyl Cyclases↗
PubMed1993

Novel isozymes of cAMP-dependent protein kinase exist in human cells due to formation of RI alpha-RI beta heterodimeric complexes.

We report that a human neoplastic B cell line (Reh) contains cAMP-dependent protein kinase (cAK) type I (cAKI), but is practically devoid of cAK type II (cAKII). However, these cells contain a novel cAKI isozyme consisting of an RI alpha-RI beta heterodimer in association with phosphotransferase activity (RI alpha RI beta C2) eluting from DEAE-cellulose columns at a salt concentration characteristic of a cAKII. Immunoprecipitation of 8-azido-[32P]cAMP-labeled extracts and DEAE fractions employing specific antibodies directed against RI alpha and RI beta clearly demonstrated the presence of RI alpha-RI beta heterodimers. RI alpha was precipitated with RI beta antiserum and vice versa. Furthermore, disruption of disulfide bridges by reduction-alkylation abolished this coimmunoprecipitation. In addition, formation of heterodimeric complexes of RI alpha and RI beta could be demonstrated in vitro using recombinant RI proteins. Finally, the presence of low levels of RI alpha-RI beta heterodimers could also be demonstrated in human peripheral blood T lymphocytes. RI alpha-RI beta heterodimers complexed with the catalytic subunit represent a novel isozyme of cAKI (RI alpha RI beta C2), which enhances the possibilities for diversification of cAMP-mediated effects.

Amino Acid Sequence↗
PubMed1993

Isolation and characterization of a human pseudogene for the regulatory subunit RI alpha of cAMP-dependent protein kinases and its sublocalization on chromosome 1.

Using a human cDNA (complementary DNA) encoding the regulatory subunit RI alpha of cAMP-dependent protein kinases (PKA) as a probe, a pseudogene for this PKA isoform was isolated from a human genomic library. The human RI alpha pseudogene was 89% similar to the open reading frame of the expressed human RI alpha at the nucleotide level. Several stop codons were found, indicating that the pseudogene does not encode a functional protein. The pseudogene also contained several frameshift mutations, small deletions, and insertions. No introns were found in the region corresponding to the open reading frame of the expressed RI alpha cDNA. Specific oligonucleotides for the RI alpha gene and pseudogene were constructed and used as primers in polymerase chain reaction (PCR) to amplify human DNA from healthy blood donors. Probing of the PCR products using oligonucleotides specific for the RI alpha gene and RI alpha pseudogene, respectively, showed the presence of both genes in the human genome. When DNA extracted from various somatic cell hybrids was amplified, it was shown that the RI alpha gene was located on human chromosome 17, whereas the RI alpha pseudogene was located in the p21-p31 region on chromosome 1. This is the first report describing a pseudogene for a subunit of cAMP-dependent protein kinases from any species.

Amino Acid Sequence↗
PubMed1993

Cellular location and age-dependent changes of the regulatory subunits of cAMP-dependent protein kinase in rat testis.

This study was undertaken to examine the expression and cellular location of the various cAMP-dependent protein kinase (PKA) subunits in different testicular cell types, using cDNA probes, isoenzyme-specific antibodies and activity measurements. Amounts of mRNA and protein were examined in cultured Sertoli cells, cultured peritubular cells, germ cells (pachytene spermatocytes, round spermatids), Leydig cell tumours as well as whole testes from rats of various ages. In Sertoli cells, there was a good correlation between the amount of mRNA and the respective immunoreactive proteins. In other types of cell, such as germ cells and Leydig tumour cells, this was not always the case. Large amounts of RII beta mRNA were found in Leydig tumour cells, whereas the amount of immunoreactive protein was low. Furthermore, large amounts of small-sized, germ cell-specific mRNAs for RI alpha (1.7 kb) and RII alpha (2.2 kb) were also found in the developing rat testis after 30 to 40 days of age, but the large amounts of mRNA were only partially reflected at the protein level. Pachytene spermatocytes and round spermatids were practically devoid of both RII alpha and RII beta protein. During spermatid differentiation, there was a decrease in RI alpha and an increase in RII alpha protein. Cell specific distribution of the various PKA subunits in testicular cell types is described. In some types of cell, discrepancies between mRNA and protein were demonstrated, which clearly suggest cell specific differences in translational efficiencies for some of these mRNAs, particularly the small-sized mRNAs for RI alpha and RII alpha in meiotic and post-meiotic germ cells.

Aging↗
PubMed1992

The C gamma subunit is a unique isozyme of the cAMP-dependent protein kinase.

There are at least three isozymes (C alpha, C beta, and C gamma) of the mammalian catalytic (C) subunit of cAMP-dependent protein kinase (PKA) (Beebe, S., Oyen, O., Sandberg, M., Froysa, A., Hansson, V., and Jahnsen, T. (1990) Mol. Endocrinol. 4, 465-475). To compare the C gamma and C alpha isozymes, the respective cDNAs were expressed in permanently transformed Kin-8 PKA-deficient Y1 adrenal cells using the mouse metallothionein promoter. The recombinant C subunits were characterized as immunoreactive, zinc-inducible, cAMP-dependent kinase activities. In contrast to C alpha, histone was a better substrate than Leu-Arg-Arg-Ala-Ser-Leu-Gly (Kemptide) for C gamma. Furthermore, C gamma histone kinase activity was not inhibited by the protein kinase inhibitor peptide (5-24 amide), which has been widely used as a PKA-specific inhibitor. The major C gamma peak (type I) eluted from DEAE-Sepharose at a higher NaCl concentration (120 mM) than the C alpha type I eluted (70 mM). C gamma and C alpha type II eluted between 220 and 240 mM NaCl. C gamma required higher concentrations of cAMP than C alpha did for dissociation from the mutant type I holoenzyme. These differences provided a basis for the separation of the mutant RI-associated isozymes on DEAE-Sepharose. Both C alpha (41-42 kDa) and C gamma (39-40 kDa) were identified by a C subunit antibody after sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblot analysis. Zinc induced the PKA-mediated rounding phenotype in C gamma and C alpha clones, thereby restoring the cells to the parent Y1 adrenal cell phenotype. Collectively, these data indicate that C gamma is an active PKA C subunit but suggest that C gamma and C alpha have different protein and peptide recognition determinants.

Adrenal Glands↗
PubMed1992

Cyclic AMP-dependent protein kinase type I mediates the inhibitory effects of 3',5'-cyclic adenosine monophosphate on cell replication in human T lymphocytes.

Human T lymphocytes were used as a model system to study the expression and roles of cAMP-dependent protein kinase isozymes (cAKI and cAKII) in cAMP-induced inhibition of cell replication. Human peripheral blood T lymphocytes expressed mRNA for the alpha-subforms (RI alpha and RII alpha) of the regulatory subunits of cAKI and cAKII and for the alpha- and beta-subforms (C alpha and C beta) of the catalytic subunits of cAK. At the protein level, RI alpha represented approximately 75% of the total R subunit activity, whereas RII alpha (phospho and dephospho forms) accounted for the remaining 25%. RII beta was not detected at either the mRNA or the protein level. The RI alpha protein was mainly (greater than 75%) cytosolic, whereas RII alpha was almost exclusively (greater than 90%) particulate associated. Treatment of proliferating T lymphocytes (activated through the CD3 cell surface marker) with 10 different cAMP analogs demonstrated that all inhibited cell replication in a concentration-dependent manner. The potency (as measured by the concentration giving 50% inhibition, IC50) of the cAMP analogs ranged from 30 microM for 8-chlorophenylthio-cAMP to 1100 microM for 8-piperidino-cAMP. A cAMP analog pair directed to activate cAKI (8-aminohexylamino-cAMP and 8-piperidino-cAMP) synergized in the inhibition of T lymphocyte proliferation, whereas a cAKII-directed cAMP analog pair (8-chlorophenylthio-cAMP and N6-benzoyl-cAMP) did not. We conclude that activation of cAKI is sufficient to inhibit T lymphocyte proliferation. The membrane-bound cAKII may mediate cAMP actions not related to cell replication.

Blotting, Northern↗
PubMed1992

Half-lives of different sized mRNAs for the PKA subunit RI alpha are regulated differently in response to inhibition of transcription and translation.

The RI alpha mRNA level is induced 3-5 times by FSH or cAMP analogs in primary cultures of rat Sertoli cells. In rat tissues, the RI alpha gene gives rise to three different mRNAs of different size: 3.2, 2.9 and 1.7 kb. In the present study we report that the 1.7 kb transcript has a shorter half-life than the two other mRNAs. In cells which had been pre-stimulated with a cAMP analog, inhibition of transcription stabilizes the two larger, but not the smaller sized RI alpha mRNA. However, in contrast, inhibition of protein synthesis stabilizes all the RI alpha mRNAs. Thus, degradation of various mRNAs coding for the same protein reveals different dependencies on transcription and translation.

Animals↗