Transcript length heterogeneity at the small heat shock protein genes of Drosophila

Berger, Edward M.; Vitek, Michael P.; Morganelli, Christine M.

doi:10.1016/0022-2836(85)90264-5

Cited by 17 publications

(3 citation statements)

References 28 publications

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“…Total radioactivity in lane 1 was equivalent to that in lane 2. Thus, what appears to be a greater concentration of RNA in the sample digested with oligo(dT) is an artifact of the collapse of all the broadly distributed, polyadenylated species (many of which were detected only on film with longer exposures) into a single band. Indeed, when the entire distribution of polyadenylated species (-30 to 160 nt) was summed, it accounted for 60% of the radioactivity in lane 1 3' uncleaved "run-on" transcripts [10].) Note also that this RNA is not expressed as well as Hsp7O at the higher temperatures (45).…”

Section: Resultsmentioning

confidence: 99%

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Preferential deadenylation of Hsp70 mRNA plays a key role in regulating Hsp70 expression in Drosophila melanogaster.

1994

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Following a standard heat shock, -40%o ofHsp7O transcripts in Drosophila melanogaster lack a poly(A) tail. Since heat shock disrupts other aspects of RNA processing, this observation suggested that heat might disrupt polyadenylation as well. We find, however, that as the temperature is increased a larger fraction of Hsp7O RNA is polyadenylated. Poly(A)-deficient Hsp7O RNAs arise not from a failure in polyadenylation but from the rapid and selective removal of poly(A) from previously adenylated transcripts. Poly(A) removal is highly regulated: poly(A) is (i) removed much more rapidly from Hsp7O RNAs than from Hsp23 RNAs, (ii) removed more rapidly after mild heat shocks than after severe heat shocks, and (iii) removed more rapidly after a severe heat shock if cells have first been conditioned by a mild heat treatment. Poly(A) seems to be removed by simple deadenylation rather than by endonucleolytic cleavage 5' of the adenylation site. During recovery from heat shock, deadenylation is rapidly followed by degradation. In cells maintained at high temperatures, however, the two processes are uncoupled and Hsp7O RNAs are deadenylated without being degraded. These deadenylated mRNAs are translated with low efficiency. Deadenylation therefore allows Hsp7O synthesis to be repressed even when degradation of the mRNA is blocked. Poly(A) tail shortening appears to play a key role in regulating Hsp7O expression.The most abundant and tightly regulated heat-inducible protein in Drosophila melanogaster is Hsp7O (47,62). Hsp7O and its relatives make up a highly conserved protein family, with eukaryotic, eubacterial, and archaebacterial members sharing at least 50% amino acid identity (27,30,47). Eukaryotes have several Hsp7O proteins. Some are constitutive and are required for normal growth, whereas others are heat inducible and help organisms cope with the toxic effects of heat. In D. melanogaster the haploid genome encodes five virtually identical heat-inducible Hsp7O proteins (32), which share -70 to 80% amino acid identity with their constitutively expressed relatives (61, 64). Consistent with their independent patterns of regulation, the 3' and 5' sequences of the constitutive genes share little or no homology with those of the heat-inducible genes.The heat- strategies are used. First, the absence of introns in the Hsp7O gene (31) allows its transcripts to circumvent the high-temperature-induced block in mRNA splicing and move rapidly into the cytoplasm (91). Second, high temperatures block the turnover of the normally short-lived Hsp7O mRNA, allowing it to accumulate very rapidly to high concentrations (67). Third, the translation of normal cellular mRNAs is inhibited at high temperatures by mechanisms that act at the levels of both initiation and elongation (8,33,45,80). Hsp7O mRNAs are translated efficiently under these conditions because special sequences in their 5' untranslated leaders allow them to circumvent the block in translation (51; for a review, see reference 46).After return to normal temperatures, hsp synthe...

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Section: Resultsmentioning

confidence: 99%

“…Second, after heat shock some heat-inducible transcripts are found to extend far beyond the usual polyadenylation site. Examples include gene 2 (63) and certain small hsp gene transcripts (10) in D.…”

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confidence: 99%

Preferential deadenylation of Hsp70 mRNA plays a key role in regulating Hsp70 expression in Drosophila melanogaster.

1994

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“…We have observed a similar phenomenon for MRP/proliferin transcripts (unpublished observation). Other occurences of measurable trimming of the poly(A) tail have been described recently in the cases of metallothionein mRNA (38) and the small heat shock protein genes of Drosophila (39).…”

Section: Discussionmentioning

confidence: 75%

A growth-responsive gene (16C8) in normal mouse fibroblasts homologous to a human collagenase inhibitor with erythroid-potentiating activity: evidence for inducible and constitutive transcripts

et al. 1986

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We present the DNA sequence of an essentially full-length cDNA clone of 16C8, a growth factor-inducible gene isolated from a mouse embryo fibroblast cDNA library. The 0.9-kb mRNA encodes an Mr 22,500 protein that has substantial homology to a human protein with the reported abilities (1) to potentiate erythroid differentiation and (2) to inhibit collagenases and other tissue metalloproteinases. The N-terminus of the predicted protein has a hydrophobic nature characteristic of secreted proteins, and two potential sites for Nlinked glycosylation are present. The cytoplasmic concentration of 16C8 mRNA is maximal in mid Gl at about 6 h after serum stimulation of quiescent fibroblasts. Northern blot analysis showed a progressive reduction in the size of the induced 16C8 transcripts with increasing time after serum stimulation. This was shown to be due to the reduction in length of the poly(A) tails. S1 analysis of the 5' portion of the mRNA revealed the presence of three different species of transcript, only one of which was inducible.

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Plant Tolerance to Heat Stress: Current Strategies and New Emergent Insights

Leone

Perrotta

Maresca

2003

Abiotic Stresses in Plants

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Transcript length heterogeneity at the small heat shock protein genes of Drosophila

Cited by 17 publications

References 28 publications

Preferential deadenylation of Hsp70 mRNA plays a key role in regulating Hsp70 expression in Drosophila melanogaster.

Preferential deadenylation of Hsp70 mRNA plays a key role in regulating Hsp70 expression in Drosophila melanogaster.

A growth-responsive gene (16C8) in normal mouse fibroblasts homologous to a human collagenase inhibitor with erythroid-potentiating activity: evidence for inducible and constitutive transcripts

Plant Tolerance to Heat Stress: Current Strategies and New Emergent Insights

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