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PubMed2003

The 3' terminal region is strictly required for clover yellow vein virus genome replication.

To identify the cis-element in the 3' terminal region of infectious cDNA required for replication of clover yellow vein virus (ClYVV), a series of mutants with duplications or deletions of the 3' terminal non-coding region (3'-NCR) of the genome that did not affect the ORFs in the genome was constructed. These were tested for infectivity, and the 3' terminal regions of their progeny RNAs were sequenced. Deletion mutants that lacked portions of the 3'-NCR were not infectious. Various mutants with duplicated 3' terminal sequences were infective only when the authentic 3' terminal sequence was restored, probably by recombination, and none of the constructs retained the original sequence in progeny viral RNA. When a coat protein gene sequence of bean yellow mosaic virus (BYMV) followed by a termination codon was introduced between the nuclear inclusion b and coat protein genes, infective progeny were generated. Sequence analyses of the progeny viruses showed that the coat protein gene was a chimera of the BYMV N-terminal and CIYVV C-terminal portions. These results suggest that the 3'-NCR of ClYVV contains cis-acting elements and is strictly required for genome replication.

3' Untranslated Regions↗

PubMed2005

A newly discovered function for RNase L in regulating translation termination.

The antiviral and antiproliferative effects of interferons are mediated in part by the 2'-5' oligoadenylate-RNase L RNA decay pathway. RNase L is an endoribonuclease that requires 2'-5' oligoadenylates to cleave single-stranded RNA. In this report we present evidence demonstrating a role for RNase L in translation. We identify and characterize the human translation termination factor eRF3/GSPT1 as an interacting partner of RNase L. We show that interaction of eRF3 with RNase L leads to both increased translation readthrough efficiency at premature termination codons and increased +1 frameshift efficiency at the antizyme +1 frameshift site. On the basis of our results, we present a model describing how RNase L is involved in regulating gene expression by modulating the translation termination process.

Carrier Proteins↗

PubMed2005

Kaposi's sarcoma-associated herpesvirus K8beta is derived from a spliced intermediate of K8 pre-mRNA and antagonizes K8alpha (K-bZIP) to induce p21 and p53 and blocks K8alpha-CDK2 interaction.

Kaposi's sarcoma-associated herpesvirus (KSHV) is a lymphotropic DNA tumor virus that induces Kaposi's sarcoma and AIDS-related primary effusion lymphoma. KSHV open reading frame 50 and K8 genes in early viral lytic infection express, respectively, a tricistronic and a bicistronic pre-mRNA, which undergo alternative splicing to create two major spliced mRNA isoforms, alpha and beta, by inclusion (beta) or exclusion (alpha) of an intron at nucleotides 75563 to 75645. This intron contains some suboptimal features, which cause the intron 5' splice site (ss) to interact weakly with U1 snRNA and the 3' ss to bind a U2 auxiliary factor, U2AF, with low affinity. Optimization of this intron in K8 (K8 intron 2) promoted the interaction of the 5' ss with U1 and the 3' ss with U2AF, resulting in a substantial increase in intron splicing. Splicing of K8 intron 2 has also been shown to be stimulated by the splicing of a downstream intron. This was confirmed by the insertion of a human beta-globin intron into the K8beta exon 3-exon 4 splice junction, which promoted splicing of K8beta intron 2 and conversion of the K8beta mRNA to the K8alpha mRNA that encodes a K-bZIP protein. Intron 2 contains a premature termination codon, yet the K8beta mRNA is insensitive to nonsense-mediated mRNA decay, suggesting that the truncated K8beta protein may have a biological function. Indeed, although the truncated K8beta protein is missing only a C-terminal leucine zipper domain from the K-bZIP, its expression antagonizes the ability of the K-bZIP to induce p53 and p21 and blocks K-bZIP-CDK2 interaction through interfering K8alpha mRNA production.

Alternative Splicing↗

PubMedDate not supplied

An estimate on the effect of point mutation and natural selection on the rate of amino acid replacement in proteins.

We outline a method for estimating quantitatively the influence of point mutations and selection on the frequencies of codons and amino acids. We show how the mutation rate, i.e., the rate of amino acid replacement due to point mutation, can be affected by the codon usage as well as by the rates of the involved base exchanges. A comparison of the mutation rates calculated from reliable values of codon usage and base exchange probabilities with those that would be expected on the basis of chance reveals a notable suppression of replacements leading to tryptophan, glutamate, lysine, and methionine, and particularly of those leading to the termination codons. If selection constraints are neglected and only mutations are taken into account, the best agreement between expected and observed frequencies of both codons and amino acids is obtained for alpha = 1.13-1.15, where (Formula: see text). The "selection values" of codons and amino acids derived by our method show a pattern that partially deviates from others in the literature. For example, the selection pressure on methionine and cysteine turns out to be much more pronounced than expected if only the discrepancies between their observed and expected occurrences in proteins are considered. To estimate to what extent randomly occurring amino acid replacements are accepted by selection, we constructed an "acceptability matrix" from the well-established matrix of accepted point mutations. On the basis of this matrix "acceptability values" of the amino acids can be defined that correlate with their selection values. We also examine the significance of mutations and selection of amino acids with respect to their physicochemical properties and functions in proteins. The conservatism of amino acid replacements with respect to certain properties such as polarity can be brought about by the mutational process alone, whereas the conservatism with respect to other relevant properties--among them all measures of bulkiness--obviously is the result of additional selectional constraints on the evolution of protein structures.

Amino Acid Sequence↗

PubMed2003

Identification of the essential and non-essential transcription units for protein synthesis, DNA replication and infectious virus production of Porcine circovirus type 1.

A plasmid-based transfection system capable of yielding infectious Porcine circovirus type 1 (PCV1) was established and mutational analysis was conducted to investigate the involvement of each viral transcription unit in protein synthesis, DNA replication and progeny virus production. During PCV1 replication in PK15 cells, twelve viral-specific RNAs are synthesized. They include the capsid protein RNA ( CR), eight Rep-associated RNAs ( Rep, Rep', Rep3a, Rep3b, Rep3c-1, Rep3c-2, Rep3c-3 and Rep3c-4), and three NS-associated RNAs ( NS462, NS642 and NS0). A stop codon introduced at the 5'-end of CR did not affect Rep-associated antigens or viral DNA synthesis. Altering the consensus dinucleotide at the splice junctions of the Rep3 RNAs and NS462 or introducing an early termination codon in Rep3c-4 and NS0 also did not have any affect on virus replication. However, mutations in Rep and Rep' caused greater than 99% reduction of protein synthesis and complete shut down of viral DNA replication. NS642 could not be assayed in this study because silent mutation at the splice junction was not possible. However, it is probably equivalent to the non-essential RNA ( NS672) of PCV type 2. Thus, only two proteins, Rep and Rep', are essential for PCV1 protein, DNA and infectious virus biosynthesis.

Animals↗

PubMed1987

High-affinity L-arabinose transport operon. Nucleotide sequence and analysis of gene products.

The nucleotide sequence of the "high-affinity" L-arabinose transport operon has been determined 3' from the regulatory region and found to contain three open reading frames designated araF, araG and araH. The first gene 3' to the regulatory region, araF, encodes the 23-residue signal peptide and the 306-residue mature form of the L-arabinose binding protein (33,200 Mr). The binding protein, which has been described elsewhere, is hydrophilic, soluble and found in the periplasm of Escherichia coli. This gene is followed by an intragenic space of 72 nucleotides, which contains a region of dyad symmetry 23 nucleotides long capable of forming an 11-member stem-loop. The second gene, designated araG, contains an open reading frame capable of encoding an equally hydrophilic protein containing 504 residues (55,000 Mr). Following a 14-nucleotide spacer, which does not appear to have any secondary structure, the third open reading frame, herein designated araH, is capable of encoding a hydrophobic protein containing 329 residues (34,000 Mr) that can only be envisioned as having an integral membrane location. 3' to araH there is a T-rich region containing a 24-nucleotide area of dyad symmetry centered 55 nucleotides from the termination codon. Analysis of the derived primary sequences of the araG and araH products indicates the nature and potential features of these components. The araG protein was found to possess internal homology between its amino and carboxyl-terminal halves, suggesting a common origin. The araG gene product has been shown to be homologous to the rbsA gene product, the hisP product, the ptsB product and the malK product, all of which presumably play similar roles in their respective transport systems. Putative ATP binding sites are observed within the regions of homology. The araH gene product has been shown to be homologous to the rbsC gene product, which is the first observed homology between two purported membrane proteins.

Amino Acids↗

PubMed1985

Lamprey fibrinogen gamma chain: cloning, cDNA sequencing, and general characterization.

A cDNA library from lamprey liver was constructed in pBR322 and screened with a synthetic mixed oligonucleotide probe, the sequence of which was based on a partial amino acid sequence of the lamprey fibrinogen gamma chain determined by conventional procedures. Among the positive clones was one containing a 600-base insert that covered the carboxy-terminal third of the chain and another with a 1950-base insert that stretched more than full length. The two inserts were sequenced by the Maxam-Gilbert procedure. The DNA sequencing was corroborated by reference to the amino acid sequences of five cyanogen bromide peptides that compose the carboxy-terminal 130 amino acids, as well as to a number of tryptic peptides from elsewhere in the molecule. The clone with the smaller insert (6G) contained 594 nucleotides (not counting G and C tails), 435 of which are coding and correspond to residues 264-408 of the gamma chain. The remaining 159 nucleotides included the terminator codon followed by a noncoding segment. The larger clone (2E) coded for 408 amino acids that could be readily aligned with the 411-residue human gamma chain. A 24-residue signal peptide adjacent to the proposed amino terminal was also inferred. The amino acid sequence of the fibrinogen gamma chain has been differentially conserved during evolution, the lamprey and human sequences being more than 70% identical in certain key regions but dropping to less than 25% in other sections, including the segment thought to be a part of the "coiled coils". Overall, the resemblance amounts to 50% identity. Of the 10 cysteines found in mammalian chains, 9 are at identical positions, but the tenth, which in mammalian fibrinogens is a part of the interdimeric bridging, is absent in the lamprey.

Amino Acid Sequence↗

PubMed1998

Two novel 1alpha-hydroxylase mutations in French-Canadians with vitamin D dependency rickets type I1.

BACKGROUND: Vitamin D dependency rickets type I (VDDR-I) is an autosomal recessive disorder in which 25-hydroxyvitamin D 1alpha-hydroxylase (1alpha-hydroxylase) activity in renal proximal tubules is deficient. VDDR-I is recognized throughout the world, but occurs more frequently in a subset of the French-Canadian population. We and others have recently cloned the human 1alpha-hydroxylase cDNA and gene, making it possible to screen for mutations. The first VDDR-I mutations were reported in one American and four Japanese patients. In this study, we screened for 1alpha-hydroxylase mutations in French-Canadian patients with VDDR-I. METHODS: The nine exons of the 1alpha-hydroxylase gene were amplified by polymerase chain reaction (PCR) from genomic DNA of four unrelated French-Canadian patients with VDDR-I and their parents, and sequenced. RESULTS: Three of the patients were homozygous for a single base-pair deletion (G) at position 262 in the cDNA that lies in exon 2, and causes a premature termination codon upstream from the putative ferredoxin- and heme-binding domains. The fourth patient was homozygous for a 7-bp insertion (CCCCCCA) at position 1323 of the cDNA that lies in exon 8, and causes a premature termination upstream from the putative heme-binding domain. In each family, obligate carriers have one copy of the mutant allele. These mutations, which could be detected by PCR-restriction fragment length polymorphism and polyacrylamide gel electrophoresis of the PCR products, were not found in 25 normal French-Canadians. CONCLUSION: We describe two novel 1alpha-hydroxylase mutations that are consistent with loss of function in four French-Canadian patients with VDDR-I and suggest that the 1alpha-hydroxylase mutations arise from more than one founder in this population.

25-Hydroxyvitamin D3 1-alpha-Hydroxylase↗

PubMed1987

Alternative processing of bovine growth hormone mRNA: nonsplicing of the final intron predicts a high molecular weight variant of bovine growth hormone.

We have detected a variant species of bovine growth hormone mRNA in bovine pituitary tissue and in a stably transfected bovine growth hormone-producing cell line. Analysis of this variant mRNA indicated that the last intervening sequence (intron D) had not been removed by splicing. Inspection of the sequence of intron D reveals an open reading frame through the entire intron, with a termination codon encountered 50 nucleotides into the fifth exon, which is shifted from the normal reading frame in this variant mRNA. If translated, this variant mRNA would encode a growth hormone-related polypeptide having 125 amino-terminal amino acids identical to wild-type growth hormone, followed by 108 carboxyl-terminal amino acids encoded by the 274 bases of intron D along with the first 50 nucleotides of exon 5. This variant polypeptide would be 42 amino acids longer than wild-type bovine growth hormone or approximately 5000 greater in molecular weight. The intron D-containing variant of bovine growth hormone mRNA was demonstrated to exist on polysomes, suggesting that this mRNA species is translated into a polypeptide. Cytosolic mRNA species containing any of the other three introns of the bovine growth hormone gene were not detectable.

Amino Acid Sequence↗

PubMed2006

[Detection of a new mutation (1343-TT) in the iduronate-2-sulfatase gene from a Chinese patient with mucopolysaccharidosis type II].

OBJECTIVE: Mutations of the iduronate-2-sulfatase (IDS) gene is the ultimate cause of Hunter syndrome. Clarification of the nature of mutations will create a necessary premise for prenatal gene diagnosis. A mucopolysaccharidosis (MPS) type II patient and his parents from an ethnic minority in Yunnan province were studied to identify their possible mutation in IDS gene to establish the basis for prenatal gene diagnosis. METHODS: The patient was a boy, 6 years and 10 months old. Urine glycosaminoglycans (GAGs) assay was used for preliminary diagnosis of the patient and his parents with the disease. The three related persons' DNA was extracted and the concentration and purity of the DNA were measured after the urine test results confirmed the diagnosis. Polymerase chain reaction-denaturing high performance liquid chromatography (PCR-DHPLC) analysis was performed to detect the position of the mutation around the hot spots of mutation in exon 9, 3, 8 of the IDS gene. DNA bidirectional direct sequencing was applied to analyze the mutation detected by PCR-DHPLC. RESULTS: The results of GAGs test showed that in the child with MPS, dermatan sulfate (DS) was positive (+++), heparan sulfate (HS) (+++), chondroitin sulfate (CS) and keratan sulfate (KS) were negative (-); while in his parents none of DS, HS, CS and KS was positive. Abnormal peaks in exon 9 of IDS gene shown by PCR-DHPLC were found in the patient. His mother had heterozygotic peaks. A new frame-mutation (1343-TT) in exon 9 of IDS gene of this patient was confirmed by DNA sequencing. The position where mutation occurred was inside codon 407 (TTT), that means two "T" deleted at position 1343 base pair (1343-TT) in cDNA of the IDS gene, caused a new frame-mutation. It caused elongation of the amino acid chain to a terminal codon TGA at position 429. Thus the peptide chain was shortened from 550 to 428 amino acids. The patient is a hemizygote of the mutation and his mother is a heterozygote. CONCLUSION: A new frame-mutation (1343-TT) on the IDS gene was identified in this study. The patient is a hemizygote and his mother is a heterozygote. The mutation (1343-TT) resulted in loss of 122 amino acids, which probably caused seriously decreased enzyme activity of IDS, and the authors speculate that this mutation may be the pathological basis of the disease. So, if the mother becomes pregnant again, a prenatal gene diagnostic test for the same mutation should be performed. Furthermore, PCR-DHPLC followed by DNA sequencing are effective methods for diagnosis, including prenatal diagnosis of MPS II.

Amino Acid Sequence↗

PubMed1987

Characterization of mouse mammary tumor virus gag-pro gene products and the ribosomal frameshift site by protein sequencing.

The synthesis of retroviral polyproteins that are the translational products of the genome-size mRNA is initiated in the upstream gag gene. The synthesis of the products of the protease gene (pro) and polymerase gene (pol) is regulated by translational suppression (in-frame read-through or frameshift) of termination codons as a strategy developed for controlling the level of replicative enzymes required only in catalytic amounts. In mouse mammary tumor virus (MMTV), three overlapping reading frames are utilized for the synthesis of gag-encoded Pr77, gag-pro-encoded Pr110, and gag-pro-pol-encoded Pr160 polyproteins. To characterize pro gene products and to determine the site of frameshift required for the synthesis of Pr110, we purified and sequenced three MMTV proteins: p14, p30, and p13. Sequence analysis showed that p14 is the basic nucleic acid-binding protein derived entirely from gag, and p13 is a product of the pro gene and has characteristic sequences of protease. A comparison of the amino acid sequences of p30 with the corresponding nucleotide sequence of proviral DNA allowed the delineation of the frameshift site utilized in vivo for the synthesis of the gag-pro-encoded fusion polyprotein Pr110. The results showed that: (i) the N-terminal 94 residues of p30 are translated from the gag frame; (ii) residue leucine-95 is specified by either the last UUG codon of gag or the overlapping CUU codon in the pro frame; and (iii) the elongation of the peptide chain from residue 96 continued to be encoded in the pro frame to the pro terminator. The possible mechanisms of frameshift and of the tRNAs involved are discussed.

Amino Acid Sequence↗

PubMed1989

Spectinomycin operon of Micrococcus luteus: evolutionary implications of organization and novel codon usage.

The complete DNA sequence of the Micrococcus luteus spectinomycin (spc) operon and its adjacent regions has been determined. The sequence has revealed the presence of genes that are homologous to those of the Escherichia coli ribosomal and related proteins, L14, L24, L5, S8, L6, L18, S5, L30, L15, and secretion protein Y (sec Y), and the gene for adenylate kinase (adk). The gene arrangement in the spc operon is essentially the same as that of E. coli except for the absence in the M. luteus spc operon of the genes for S14 and X protein that exist in the E. coli spc operon. SecY and adk seem to be composed of another operon (adk operon) with at least an open reading frame. The deduced amino acid sequences for these ribosomal proteins are well conserved among the two species (40-65% identity). Reflecting the high genomic guanine and cytosine (GC) content of M. luteus (74%), the codon usage of the genes is extremely biased toward use of G and C, about 94% of the codon third positions being G or C. Seven codons, AUA, AAA, AGA, UUA, GUA, CUA, and CAA, all of which have A at the codon third positions, are completely absent in the M. luteus genes examined. Out of 11 genes in the M. luteus spc and adk operons, 5 (10) use GUG (UGA) and 6 (1) use AUG (UAA) as an initiation (termination) codon.

Amino Acid Sequence↗

PubMed1994

Expression of two variants of the human mu opioid receptor mRNA in SK-N-SH cells and human brain.

A partial mu opioid receptor gene was isolated from a human genomic library using a mouse delta opioid receptor cDNA as a probe. Using information from this genomic clone and the published human mu receptor, MOR1, a cDNA was isolated from SK-N-SH mRNA that codes for a variant of the MOR1 mRNA, MOR1A. The presence of MOR1A is also shown in human brain using RT-PCR. MOR1A differs from MOR1 in that the 3' terminal intron has not been removed. An in-frame termination codon is found four amino acids after the 5' consensus splice site, making MOR1A eight amino acids shorter than MOR1. Both receptors show similar ligand binding and coupling to cAMP in CHO-K1 cells. The C-terminal differences between MOR1 and MOR1A could have effects on receptor coupling or receptor transport and localization.

Alternative Splicing↗

PubMed1988

The existence of two genes between infB and rpsO in the Escherichia coli genome: DNA sequencing and S1 nuclease mapping.

A number of genes encoding proteins involved in transcription and translation are clustered between 68 and 69 minutes on the Escherichia coli genome map and are transcribed clockwise as two operons: the metY operon, containing metY, P15A, nusA, infB; and about a kilobase further downstream, the rpsO and pnp operon. The DNA sequence between infB and rpsO was determined and two open reading frames were detected which code for proteins of 15,200 (P15B) and 35,091 (P35) daltons. Maxicell analysis showed a relatively strong expression of P15B whereas P35 was synthesized more weakly. An overlap of the termination codon of P15B and the initiator codon for P35 suggests that translation of P15B and P35 may be coupled. S1 nuclease mapping of in vivo transcripts between infB and rpsO provided no evidence for major promoters but detected a moderately efficient rho-independent terminator between infB and P15B. The results indicate that P15B and P35 are expressed as part of the metY operon, but that some transcriptional read through into the rpsO operon also occurs, thereby, functionally linking the expression of these two complex systems.

Amino Acid Sequence↗

PubMed1992

Truncation of the human immunodeficiency virus type 1 transmembrane glycoprotein cytoplasmic domain blocks virus infectivity.

Human immunodeficiency virus type 1 contains a transmembrane glycoprotein with an unusually long cytoplasmic domain. To determine the role of this domain in virus replication, a series of single nucleotide changes that result in the insertion of premature termination codons throughout the cytoplasmic domain has been constructed. These mutations delete from 6 to 192 amino acids from the carboxy terminus of gp41 and do not affect the amino acid sequence of the regulatory proteins encoded by rev and tat. The effects of these mutations on glycoprotein biosynthesis and function as well as on virus infectivity have been examined in the context of a glycoprotein expression vector and the viral genome. All of the mutant glycoproteins were synthesized, processed, and transported to the cell surface in a manner similar to that of the wild-type glycoprotein. With the exception of mutants that remove the membrane anchor domain, all of the mutant glycoproteins retained the ability to cause fusion of CD4-bearing cells. However, deletion of more than 19 amino acids from the C terminus of gp41 blocked the ability of mutant virions to infect cells. This defect in virus infectivity appeared to be due at least in part to a failure of the virus to efficiently incorporate the truncated glycoprotein. Similar data were obtained for mutations in two different env genes and two different target cell lines. These results indicate that the cytoplasmic domain of gp41 plays a critical role during virus assembly and entry in the life cycle of human immunodeficiency virus type 1.

Animals↗

PubMed1991

Molecular cloning and nucleotide sequencing of the coat protein gene of citrus tristeza virus.

Citrus tristeza virus (CTV) contains approximately 20,000 bases of positive-sense ssRNA, encapsidated by a coat protein of approximately 25,000 Mr that has previously been reported to consist of at least two size variants, cp1 and cp2. In the present study, a cDNA library of the T36 isolate of CTV was prepared in a protein expression vector and screened with a polyclonal antibody against the coat protein. Five immunopositive clones produced proteins in Escherichia coli that reacted with monoclonal as well as polyclonal antibodies to the CTV coat protein. Nucleotide sequence analysis of a region common to the five clones revealed the presence of a 669 nucleotide open reading frame flanked by numerous in-frame termination codons. The encoded protein has a predicted Mr of 24,909 and an amino acid composition consistent with that previously reported for the CTV coat protein. Comparison of the predicted amino acid sequence of the coat protein with the amino-terminal sequences of cp1 and cp2 indicated that these coat protein species arise from the same primary translation product, as a result of post-translational proteolysis at sites approximately 12 to 15 and 26 amino acids from the amino terminus respectively. These results are the first reported cloning and sequencing of a CTV gene and provide evidence that CTV may be translated using subgenomic RNA.

Amino Acid Sequence↗

PubMed2003

Amino acid mutations in the replicase protein nsP3 of Semliki Forest virus cumulatively affect neurovirulence.

It has been shown previously that an avirulent Semliki Forest virus (SFV) clone, rA774, engineered to carry the nsP3 gene of the virulent clone SFV4 becomes highly neurovirulent and is lethal for adult BALB/c mice. rA774, like several other alphaviruses, has an opal termination codon close to the 5' end of nsP3 (aa 469), while SFV4 has an arginine residue at this position. Mutation of the opal codon to an arginine residue increases the virulence of rA774 but does not reconstruct the severe neurovirulence of SFV4. Additionally, nsP3 amino acid sequences differ between these two strains by eight amino acids and by a deletion of seven amino acids in the C-terminal third of rA774 nsP3. This study shows that neurovirulence can be reconstituted gradually by exchanging individual amino acids and is fully retained when combinations of two nsP3 mutations, V(11)-->I and L(201)-->F, V(11)-->I and D(249)-->N, A(48)-->E and G(70)-->A or T(435)-->A and F(442)-->L, are introduced into an rA774 derivative carrying R(469). The critical role of the arginine codon for neurovirulence was confirmed further by the acquisition of a fully lethal phenotype following the introduction of R(469) into a moderately virulent rA774 recombinant carrying the SFV4 nsP1 and nsP2 genes. In conclusion, virulence determinants in SFV are distributed over a wide region of the nonstructural genes.

Alphavirus Infections↗

PubMed1993

The 3' half of the mouse mammary tumor virus orf gene is not sufficient for its superantigen function in transgenic mice.

The Mouse Mammary Tumor Virus (MMTV) long terminal repeat contains an open reading frame (orf) of 960 nucleotides encoding a 36 kDa polypeptide with a putative transmembrane domain and five N-glycosylation sites in the N-terminal part of the protein. Transgenic mice bearing either the complete or the 3' terminal half of the orf sequence of MMTV-GR under the control of the SV40 promoter were raised. As shown previously by FACS analysis transgenic mice which express the complete orf gene have a significant deletion of V beta 14 expressing T cells at 6 weeks of age. Here we show that no clonal deletion of V beta 14 bearing T cells takes place in transgenic mice that contain orf sequences from the fifth ATG to the termination codon. The pattern of tissues expressing the truncated transgene was studied by the Polymerase Chain Reaction (PCR) and was very similar to the one obtained in the V beta 14 deleting animals. These data suggest that the amino-terminal portion of the ORF protein (pORF) is required for a superantigen function, while our previous data indicated that determinants from the carboxy-terminus play an important role for TCR V beta specificity.

Amino Acid Sequence↗