The gene family encoding the mouse ribosomal protein L32 contains a uniquely expressed intron-containing gene and an unmutated processed gene

The family of approximately 16 genes encoding the mouse ribosomal protein L32 has been characterized by an analysis of a representative set of genomic clones. Surprisingly, this family contains only a single expressed intron-containing gene. This gene, termed rpL32 , has been completely sequenced and found to possess certain novel features including the presence in two of its introns of a sequence with high homology to the 5' end of U1 snRNA and a 5' terminal region exceptionally rich in pyrimidines. Most of the other members of the L32 family appear to be processed genes, some of which are identical or very similar to the rpL32 gene, except for the lack of introns. One unmutated gene was found to be integrated 28 nucleotides downstream of a canonical TATA box. However, despite this feature, the gene does not seem to be expressed, as judged by its extent of methylation compared to the expressed rpL32 gene.     

Surfeit locus gene homologs are widely distributed in invertebrate genomes.

The mouse Surfeit locus contains six sequence-unrelated genes (Surf-1 to -6) arranged in the tightest gene cluster so far described for mammals. The organization and juxtaposition of five of the Surfeit genes (Surf-1 to -5) are conserved between mammals and birds, and this may reflect a functional or regulatory requirement for the gene clustering. We have undertaken an evolutionary study to determine whether the Surfeit genes are conserved and clustered in invertebrate genomes. Drosophila melanogaster and Caenorhabditis elegans homologs of the mouse Surf-4 gene, which encodes an integral membrane protein associated with the endoplasmic reticulum, have been isolated. The amino acid sequences of the Drosophila and C. elegans homologs are highly conserved in comparison with the mouse Surf-4 protein. In particular, a dilysine motif implicated in endoplasmic reticulum localization of the mouse protein is conserved in the invertebrate homologs. We show that the Drosophila Surf-4 gene, which is transcribed from a TATA-less promoter, is not closely associated with other Drosophila Surfeit gene homologs but rather is located upstream from sequences encoding a homolog of a yeast seryl-tRNA synthetase protein. There are at least two closely linked Surf-3/rpL7a genes or highly polymorphic alleles of a single Surf-3/rpL7a gene in the C. elegans genome. The chromosomal locations of the C. elegans Surf-1, Surf-3/rpL7a, and Surf-4 genes have been determined. In D. melanogaster the Surf-3/rpL7a, Surf-4, and Surf-5 gene homologs and in C. elegans the Surf-1, Surf-3/rpL7a, Surf-4, and Surf-5 gene homologs are located on completely different chromosomes, suggesting that any requirement for the tight clustering of the genes in the Surfeit locus is restricted to vertebrate lineages.     

HzAm1细胞rpL13基因的序列分析及病毒感染对其转录水平的影响

从美洲棉铃虫细胞(HzAM1)中克隆了核糖体大亚基蛋白L13(RibosomalproteinL13,RpL13)的cDNA及其基因组DNA序列,并进行了序列分析。其编码框为666bp,无内含子,预测编码大小约为25kDa的蛋白。通过与其它15种动物的RpL13编码框序列进行进化分析,发现聚类结果与传统物种分类一致。转录研究表明,棉铃虫核型多角体病毒(Helicoverpaarmigerasinglenucleocapsidnucleopolyhedrovirus,HaSNPV)感染HzAm1后使rpL13在细胞内的转录水平降低,在病毒感染后96h,rpL13mRNA的拷贝数降到对照健康细胞的8%。     

The alpha1-microglobulin/bikunin gene: characterization in mouse and evolution.

The 129Sv mouse gene coding for the alpha1-microglobulin/bikunin precursor has been isolated and characterized. The 11kb long gene contains ten exons, including six 5'-exons coding for alpha1-microglobulin and four 3'-exons encoding bikunin. Exon 7 also codes for the tribasic tetrapeptide RARR which connects the alpha1-microglobulin and bikunin parts. The sixth intron, which separates the alpha1-microglobulin and bikunin encoding parts, was compared in the human, mouse and a fish (plaice) gene. The size of this intron varies considerably, 6.5, 3.3 and 0.1kb in man, mouse and plaice, respectively. In all three genes, this intron contains A/T-rich regions, and retroposon elements are found in the first two genes. This indicates that this sixth intron is an unstable region and a hotspot for recombinational events, supporting the concept that the alpha1-microglobulin and bikunin parts of this gene are assembled from two ancestral genes. Finally, the nonsynonymous nucleotide substitution rate of the gene was determined by comparing coding sequences from ten vertebrate species. The results indicate that the alpha1-microglobulin part of the gene has evolved faster than the bikunin part.     

A revision of the human XIST gene organization and structural comparison with mouse Xist

The XIST gene plays an essential role in X Chromosome (Chr) inactivation during the early development of female humans. It is believed that the XIST gene, not encoding a protein, functions as an RNA. The XIST cDNA is unusually long, as its full length is reported to be 16.5 kilobase pairs (kb). Here, comparison of sequences from the genomic interval downstream to the 3′ end of the human XIST gene against the human EST database brought to light a number of human EST sequences that are mapped to the region. Furthermore, PCR amplification of human cDNA libraries and RNA fluorescence in situ hybridization (RNA-FISH) demonstrate that the human XIST gene has additional 2.8 kb downstream sequences which have not been documented as a part of the gene. These data show that the full-length XIST cDNA is, in fact, 19.3 kb, not 16.5 kb as previously reported. The newly defined region contains an intron that may be alternatively spliced and seven polyadenylation signal sequences. Sequences in the newly defined region show overall sequence similarity with the 3′ terminal region of mouse Xist, and three subregions exhibit quite high sequence conservation. Interestingly, the new intron spans the first two subregions that are absent in one of the two isoforms of mouse Xist. Taken together, we revise the structure of human XIST cDNA and compare cDNA structures between human and mouse XIST/Xist. Received: 3 August 1999 / Accepted: 15 November 1999     

Structure and evolutionary origin of the gene encoding mouse NF-M, the middle-molecular-mass neurofilament protein

We describe the complete sequence of the gene encoding mouse NF-M, the middle-molecular-mass neurofilament protein. The coding sequence is interrupted by two intervening sequences which align perfectly with the first two intervening sequences in the gene encoding NF-L (the low-molecular-mass neurofilament protein); there is no intron in the gene encoding NF-M corresponding to the third intron in NF-L. Therefore, both the number of introns and their arrangement in the genes coding NF-L and NF-M contrast sharply with the number and arrangement of introns in the genes of known sequence, encoding other members of the intermediate filament multigene family (desmin, vimentin, glial fibrillary acidic protein and the acidic and basic keratins); with the exception of a single truncated keratin gene that lacks an encoded tailpiece, these genes all contain eight introns, of which at least six are placed at homologous locations. Assuming the existence of a primordial intermediate filament gene containing most (if not all) the introns found in contemporary non-neurofilament intermediate filament genes, it seems likely that an RNA-mediated transposition event was involved in the generation of an ancestral gene encoding the NF polypeptides. A combination of insertional transposition and gene-duplication events could then explain the anomalous number and placement of introns within these genes. Consistent with this notion, we show that the genes encoding NF-M and NF-L are linked.     

The complete sequence of the mouse skeletal alpha-actin gene reveals several conserved and inverted repeat sequences outside of the protein-coding region.

The complete nucleotide sequence of a genomic clone encoding the mouse skeletal alpha-actin gene has been determined. This single-copy gene codes for a protein identical in primary sequence to the rabbit skeletal alpha-actin. It has a large intron in the 5'-untranslated region 12 nucleotides upstream from the initiator ATG and five small introns in the coding region at codons specifying amino acids 41/42, 150, 204, 267, and 327/328. These intron positions are identical to those for the corresponding genes of chickens and rats. Similar to other skeletal alpha-actin genes, the nucleotide sequence codes for two amino acids, Met-Cys, preceding the known N-terminal Asp of the mature protein. Comparison of the nucleotide sequences of rat, mouse, chicken, and human skeletal muscle alpha-actin genes reveals conserved sequences (some not previously noted) outside of the protein-coding region. Furthermore, several inverted repeat sequences, partially within these conserved regions, have been identified. These sequences are not present in the vertebrate cytoskeletal beta-actin genes. The strong conservation of the inverted repeat sequences suggests that they may have a role in the tissue-specific expression of skeletal alpha-actin genes.     

Structure and chromosomal localization of the gene for the oligodendrocyte-myelin glycoprotein

Utilizing a cDNA clone encoding the oligodendrocyte-myelin glycoprotein (OMgp) to screen a human genomic DNA library, we have obtained a clone that contains the OMgp gene. The genomic clone was restriction mapped and the OMgp gene and its 5' and 3' flanking regions were sequenced. A single intron is found in the 5' untranslated region of the gene, while the coding region is uninterrupted by an intron. This placement of a single intron in the OMgp gene is identical to that of the gene for the alpha-chain of platelet glycoprotein Ib, which, along with OMgp, belongs to a family of proteins sharing two distinct structural domains: an NH2-terminal cysteine-rich domain and an adjacent domain of tandem leucine-rich repeats. Hence, it is possible that this family of proteins is not only related in terms of primary structure, but also through similar gene structure. Sequence comparison of the 5' and 3' flanking regions did not reveal striking similarities to other DNA sequences, and no obvious promoter elements were noted. By hybridization of the genomic clone to metaphase cells, we have localized the human OMgp gene to chromosome 17 bands q11-12, a region to which the neurofibromatosis type 1 gene has been previously mapped.     

Genomic structure and chromosome location of the gene encoding mouse CD59

The gene encoding the mouse analogue of the human complement regulator CD59 was cloned using a combination of long range PCR and genomic library screening. Sequence obtained showed that its genomic structure closely resembled that of the human CD59 gene, comprising 4 exons, each separated by a long intron region. The sizes of introns and exons were comparable to those of the human gene with the exception of the third intron which is 2.5 kb in the mouse compared to 7 kb in the human gene. All exon/intron boundaries conformed to the GT-AG rules for splicing. Radiation hybrid mapping localised mouse Cd59 between D2Mit333 and D2Mit127 on chromosome 2, a region homologous with human chromosome 11p13 where the human CD59 gene is localised. These data have permitted the construction of a gene targeting vector for the generation of transgenic mice deficient in CD59.