Ubiquitln expression inNeurospora crassa: cloning and sequencing of a polyubiquitin gene

Abstract

We have cloned and sequenced a polyubiquitin gene from Neurospora crassa that is organized in a four repeat-tandem array. The first repeat contains a small intron and the last is fused to an extra glutamine codon. In Northern blots, two RNA species of 1.3 kb and 0.7 kb hybridize to the isolated clone. The larger ubiquitin (UBI) transcript accumulates after partial inhibition of protein synthesis with cycloheximide, and the smaller one preferentially accumulates in conidia after germination. Unexpectedly, constitutive expression of UBI transcripts in exponentially grown mycelia is not altered by heat-shock or exposure to arsenite.

The intron of Arabidopsis thaliana polyubiquitin genes is conserved in location and is a quantitative determinant of chimeric gene expression

“…There are only two exceptions among all polyubiquitin genes described to date: a 50 bp intron in four of eleven repeats of the Caenorhabditis ubiquitin gene UBiA [ 19], and a 69 bp intron in one of four repeats in a Neurospora polyubiquitin gene [44]. However, more polyubiquitin genes share the property of introns in the 5'-untranslated region.…”

Heat Shock Proteins and the Stress Response

“…Of the four genes for ubiquitin that are expressed by exponentially growing S. cerevisiae (Ozkaynak et al 1987), heat shock induces only the UBI4, which encodes a fusion protein with five ubiquitin repeats (Finley et al 1987). The polyubiquitin gene of N. crassa is composed of four ubiquitin repeats, but its expression is not induced by heat shock or other stresses (Taccioli et al 1989). A functional UBI4 gene is also required for S. cerevisiae sporulation and for the maintenance of viable spores (Finley et al 1987;Tanaka et al 1988).…”

Changes in Three Types of Ubiquitin mRNA and Ubiquitin-protein Conjugate Levels During Lens Development

“…Polyubiquitin genes are up-regulated in response to stress in some (Bond and Schlesinger, 1985;Finley et al, 1987;Christensen and Quail, 1989), but not all (Kirchhoff et al, 1988;Taccioli et al, 1989;Graham et al, 1989;Jones et al, 1995;Samuels and Attaix, 2000) organisms and tissues. Up-regulation of polyubiquitin has also been reported during normal programmed cell death (Myer and Schwartz, 1996) and cell reorganization in plants (Durr et al, 1993).…”