Specific alanine‐tRNA species associated with fibroin biosynthesis in the posterior silk‐gland of <i>Bombyx mori</i> L.

Meza, Laura Jaramillo; Araya, Alejandro; León, Gloria; Krauskopf, Manuel; Siddiqui, M.A.Q.; Garel, Jean‐Pierre

doi:10.1016/0014-5793(77)80246-9

Cited by 47 publications

(18 citation statements)

References 18 publications

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“…Translational efficiency in these cells is maximized by the quantitative adaptation of the tRNA population to the composition of fibroin: 44% glycine, 29% alanine, and 12% serine (5,29,30,42). In the case of tRNA Ala , enrichment is achieved both by increasing the level of the constitutive type of tRNA Ala (tRNA C Ala ) and by synthesizing an additional, silk gland-specific, type (tRNA SG Ala ) (31,44). In vitro studies of representative tRNA C Ala and tRNA SG Ala genes have revealed transcription properties consistent with the patterns of tRNA C Ala and tRNA SG Ala accumulation in vivo.…”

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TATA-Binding Protein–TATA Interaction Is a Key Determinant of Differential Transcription of Silkworm Constitutive and Silk Gland-Specific tRNA^Ala Genes

Ouyang

Martinez

Young

et al. 2000

Molecular and Cellular Biology

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We have investigated the contribution of specific TATA-binding protein (TBP)-TATA interactions to the promoter activity of a constitutively expressed silkworm tRNA C Ala gene and have also asked whether the lack of similar interactions accounts for the low promoter activity of a silk gland-specific tRNA SG Ala gene. We compared TBP binding, TFIIIB-promoter complex stability (measured by heparin resistance), and in vitro transcriptional activity in a series of mutant tRNA C Ala promoters and found that specific TBP-TATA contacts are important for TFIIIB-promoter interaction and for transcriptional activity. Although the wild-type tRNA C Ala promoter contains two functional TBP binding sequences that overlap, the tRNA SG Ala promoter lacks any TBP binding site in the corresponding region. This feature appears to account for the inefficiency of the tRNA SG Ala promoter since provision of either of the wild-type TATA sequences derived from the tRNA C Ala promoter confers robust transcriptional activity. Transcriptional impairment of the wild-type tRNA SG Ala gene is not due to reduced incorporation of TBP into transcription complexes since both the tRNA C Ala and tRNA SG Ala promoters form transcription complexes that contain the same amount of TBP. Thus, the deleterious consequences of the lack of appropriate TBP-TATA contacts in the tRNA SG Ala promoter must come from failure to incorporate some other essential transcription factor(s) or to stabilize the complete complex in an active conformation.The silkworm Bombyx mori provides a clear example of regulated tRNA gene expression. The demand for fibroin, the principal protein of silk, requires highly efficient transcription and translation of the fibroin gene in cells of the silk gland. Translational efficiency in these cells is maximized by the quantitative adaptation of the tRNA population to the composition of fibroin: 44% glycine, 29% alanine, and 12% serine (5,29,30,42). In the case of tRNA Ala , enrichment is achieved both by increasing the level of the constitutive type of tRNA Ala (tRNA C Ala ) and by synthesizing an additional, silk gland-specific, type (tRNA SG Ala ) (31,44). In vitro studies of representative tRNA C Ala and tRNA SG Ala genes have revealed transcription properties consistent with the patterns of tRNA C Ala and tRNA SG Ala accumulation in vivo. That is, in a variety of extracts from non-silk gland cells, the tRNA C Ala gene directs transcription much more efficiently than does the tRNA SG Ala gene, but in concentrated extracts from silk gland, the two genes are equally efficient (60). To understand how these two genes are differentially regulated, we have investigated the basis of the transcriptional impairment of the tRNA SG Ala gene that is observed under typical in vitro conditions. Transcription of silkworm tRNA Ala genes is driven by both internal and external promoter elements (26,36,56). The critical difference between the tRNA C Ala and tRNA SG Ala genes is in the interaction of their 5Ј flanking promoter elements with the transcri...

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TATA-Binding Protein–TATA Interaction Is a Key Determinant of Differential Transcription of Silkworm Constitutive and Silk Gland-Specific tRNA^Ala Genes

Ouyang

Martinez

Young

et al. 2000

Molecular and Cellular Biology

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“…While RNA Pol III is responsible for the synthesis of most small cytoplasmic and some small nuclear RNAs (reviewed in references 6 and 18), only a few genes are known to be transcribed by this enzyme in either a tissuespecific or developmentally specific manner. Examples include the oocyte-specific and somatic 5S RNA genes of Xenopus laevis (4), the tRNA Ala gene of Bombyx mori (41,56), and the primate neural cell-specific BC200 RNA (37, 63).The initial studies on Pol III-transcribed (class III) genes defined highly conserved intragenic sequences as being both necessary and sufficient for transcription (3,11,15,17,20,24,49,52). These intragenic promoters are present in the majority of class III genes, including tRNA, adenovirus VA RNA, and the Epstein-Barr virus EBER RNA genes, as well as certain repetitive sequences, and contain two noncontiguous domains, the A and B boxes (reviewed in references 6 and 18).…”

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BC1 RNA: Transcriptional Analysis of a Neural Cell-Specific RNA Polymerase III Transcript

Martignetti

Brosius

1995

Molecular and Cellular Biology

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Rodent BC1 RNA represents the first example of a neural cell-specific RNA polymerase III (Pol III) transcription product. By developing a rat brain in vitro system capable of supporting Pol III-directed transcription, we showed that the rat BC1 RNA intragenic promoter elements, comprising an A box element and a variant B box element, as well as its upstream region, containing octamer-binding consensus sequences and functional TATA and proximal sequence element sites, are necessary for transcription. The BC1 B box, lacking the invariant A residue found in the consensus B boxes of tRNAs, represents a functionally related and possibly distinct promoter element. The transcriptional activity of the BC1 B box element is greatly increased, in both a BC1 RNA and a chimeric tRNA Leu gene construct, when the BC1 5 flanking region is present and is appropriately spaced. Moreover, a tRNA consensus B-box sequence can efficiently replace the BC1 B box only if the BC1 upstream region is removed. These interactions, identified only in a homologous in vitro system, between upstream Pol II and intragenic Pol III promoters suggest a mechanism by which the tissue-specific BC1 RNA gene and possibly other Pol III-transcribed genes can be regulated.Rodent BC1 RNA is a small, developmentally regulated, cytoplasmic RNA present in the somatic and dendritic compartments of a distinct subset of central and peripheral nervous system neurons (59, 60). This neural cell-specific RNA is most likely functional, since the single-copy rat BC1 RNA gene, which evolved from a tRNA Ala molecule (10, 36), and its neural cell-specific expression pattern have been conserved in rodents for at least 55 million years (10,35,36,38). It has been hypothesized that this nontranslated RNA, as part of a ribonucleoprotein complex, plays a role in the pre-or posttranslational events in neural postsynaptic compartments (60).Neural cell-specific BC1 RNA represents a unique model for transcriptional studies in that it is transcribed by RNA polymerase III (Pol III). While RNA Pol III is responsible for the synthesis of most small cytoplasmic and some small nuclear RNAs (reviewed in references 6 and 18), only a few genes are known to be transcribed by this enzyme in either a tissuespecific or developmentally specific manner. Examples include the oocyte-specific and somatic 5S RNA genes of Xenopus laevis (4), the tRNA Ala gene of Bombyx mori (41,56), and the primate neural cell-specific BC200 RNA (37, 63).The initial studies on Pol III-transcribed (class III) genes defined highly conserved intragenic sequences as being both necessary and sufficient for transcription (3,11,15,17,20,24,49,52). These intragenic promoters are present in the majority of class III genes, including tRNA, adenovirus VA RNA, and the Epstein-Barr virus EBER RNA genes, as well as certain repetitive sequences, and contain two noncontiguous domains, the A and B boxes (reviewed in references 6 and 18). It is now evident that (i) numerous Pol III genes require (in addition to their intragenic promoters...

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“…One class encodes tRNA la, which is common to all cell types; the other encodes tRNAsAGa, which is restricted to cells of the silk gland (21,30).…”

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Silk gland-specific tRNA(Ala) genes interact more weakly than constitutive tRNA(Ala) genes with silkworm TFIIIB and polymerase III fractions.

Sullivan¹,

Young²,

White³

et al. 1994

Mol. Cell. Biol.

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Constitutive and silk gland-specific tRNAAI" genes from silkworms have very different transcriptional properties in vitro. Typically, the constitutive type, which encodes tRNAVa, directs transcription much more efficiently than does the silk gland-specific type, which encodes tRNA,. We think that the inefficiency of the tRNAsAG gene underlies its capacity to be turned off in non-silk gland cells. An economical model is that the tRNASAGa promoter interacts poorly, relative to the tRNAA'a promoter, with one or more components of the basal transcription machinery. As a consequence, the tRNASAsG gene directs the formation of fewer transcription complexes or of complexes with reduced cycling ability. Here we show that the difference in the number of active transcription complexes accounts for the difference in tRNAA3la and tRNASAsG transcription rates. To determine whether a particular component of the silkworm transcription machinery is responsible for reduced complex formation on the tRNASAG gene, we measured competition by templates for defined fractions of this machinery.We find that the tRNAsG gene is greatly impaired, in comparison with the tRNAcA'a gene, in competition for either TFIIIB or RNA polymerase III. Competition for each of these fractions is also strongly influenced by the nature of the 5' flanking sequence, the promoter element responsible for the distinctive transcriptional properties of tRNAAa and tRNAtIa genes. These results suggest that differential interaction with TFIIIB or

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Specific alanine‐tRNA species associated with fibroin biosynthesis in the posterior silk‐gland of Bombyx mori L.

Cited by 47 publications

References 18 publications

TATA-Binding Protein–TATA Interaction Is a Key Determinant of Differential Transcription of Silkworm Constitutive and Silk Gland-Specific tRNA^Ala Genes

TATA-Binding Protein–TATA Interaction Is a Key Determinant of Differential Transcription of Silkworm Constitutive and Silk Gland-Specific tRNA^Ala Genes

BC1 RNA: Transcriptional Analysis of a Neural Cell-Specific RNA Polymerase III Transcript

Silk gland-specific tRNA(Ala) genes interact more weakly than constitutive tRNA(Ala) genes with silkworm TFIIIB and polymerase III fractions.

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Specific alanine‐tRNA species associated with fibroin biosynthesis in the posterior silk‐gland of Bombyx mori L.

Cited by 47 publications

References 18 publications

TATA-Binding Protein–TATA Interaction Is a Key Determinant of Differential Transcription of Silkworm Constitutive and Silk Gland-Specific tRNAAla Genes

TATA-Binding Protein–TATA Interaction Is a Key Determinant of Differential Transcription of Silkworm Constitutive and Silk Gland-Specific tRNAAla Genes

BC1 RNA: Transcriptional Analysis of a Neural Cell-Specific RNA Polymerase III Transcript

Silk gland-specific tRNA(Ala) genes interact more weakly than constitutive tRNA(Ala) genes with silkworm TFIIIB and polymerase III fractions.

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TATA-Binding Protein–TATA Interaction Is a Key Determinant of Differential Transcription of Silkworm Constitutive and Silk Gland-Specific tRNA^Ala Genes

TATA-Binding Protein–TATA Interaction Is a Key Determinant of Differential Transcription of Silkworm Constitutive and Silk Gland-Specific tRNA^Ala Genes