The nucleotide sequence of a 2·1 kb fragment from chromosome VI of Saccharomyces cerevisiae identifies a tRNAGly gene,part of a delta element and a palindromic sequence

The nucleotide sequence was determined of a 2·1 kb DNA fragment located at approximately 35 kb to the right of the centromere of chromosome VI from Saccharomyces cerevisiae. Analysis revealed the presence of a tRNA^GLy gene, part of a delta element and a remarkable palindromic sequence. The longest open reading frame found encodes a putative protein of 195 amino acids. Although the fragment was isolated by hybridization to a human diacylglycerol kinase cDNA, no evidence was obtained for the presence of a gene encoding diacylglycerol kinase.     

Sequence and function analysis of a 2·73 kb fragment of Saccharomyces cerevisiae chromosome II

The nucleotide sequence of a fragment of 2728 base pairs of Saccharomyces cerevisiae chromosome II has been determined. The sequence contains two open reading frames, one of them being incomplete. Deletion mutants of YBR11.21 are viable. YBR11.20 is identical to the recessive omnipotent suppressor SUP45 (SUP1).     

Nd:YAG激光微束切割大麦染色体及染色体片段的分离

以适当参数的ＮｄＹＡＧ激光微束切割大麦７Ｈ染色体后再利用微细玻璃针挑取了７ＨＳ端部片段并放入Ｅｐｐｅｎｄｏｒｆ管中，建立了一种激光微束与玻璃针结合使用微切割、微分离植物染色体片段的方法，为今后植物染色体特定区域ＤＮＡ的微克隆技术提供了一种新的方法     

Tubulin heterodimers remain functional for one cell cycle after the inactivation of tubulin‐folding cofactor D in fission yeast cells

Tubulin‐folding cofactor D plays a major role in the formation of functional tubulin heterodimers, the subunits of microtubules (MTs) that are essential for cell division. Previous work has suggested that, in Schizosaccharomyces pombe, cofactor D function is required during G₁ or S phases of the cell cycle, and when it fails to function due to the temperature‐sensitive mutation alp1‐t1, cells are unable to segregate their chromosomes in the subsequent mitosis. Here we report that another mutation in the cofactor D gene, alp1‐1315, causes failures in either the first or second mitosis in cells synchronized in G₁ or G₂ phases, respectively. Other results, however, suggest that the kinetics of viability loss in these mutants does not depend on progression through the cell cycle. When cofactor D function is perturbed in cells blocked in G₂, cytoplasmic MTs appear normal for 2–3 h but thereafter they disintegrate quickly, so that only a few short MTs remain. These residual MTs are, however, stably maintained, suggesting that they do not require active cofactor D function. The abrupt disassembly of MT cytoskeleton at restrictive temperature in non‐cycling cofactor D mutant cells strongly suggests that the life‐span of folded tubulin dimers might be downregulated. Indeed, this period is significantly shorter than the previously determined dissociation time of bovine tubulins in vitro. The death of mutant cells occurs inevitably after 2–3 h at restrictive temperature in the following mitosis, and is explained by the idea that MT structures formed in the absence of cofactor D cannot support normal cell division. Copyright © 2009 John Wiley & Sons, Ltd.     

Computer-aided integrating microdensitometry and specimen imaging with the Vickers M85A

A Vickers M85A flying-spot microdensitometer has been linked to a standard BBC model B microcomputer with a commercially available interface, and programs developed in which the computer controls step-wise scanning of the specimen. At each image point thirty-two absorbance readings are made and the average value is stored in the computer memory at 8-bit resolution; a complete 48×48 raster takes less than 5 s. An image of the specimen displayed on the monitor uses eight different pseudo-grey-level characters, and the manner in which the 256 possible absorbance values are represented on the screen can be altered by the user. A mask of arbitrary shape and size, drawn on the screen under key-board control, makes it possible to measure the integrated absorbance of even small, irregular and closely packed specimens such as individual bands in Drosophila polytene chromosomes. The coefficient of variation of repeated measurements of a Feulgen-stained frog nucleus is typically better than 1%. Displayed images can be printed on a dot-matrix printer, and data stored on disc for subsequent analysis. The techniques can readily be modified and adapted for other purposes, some of which are briefly discussed.     

XIII. Yeast mapping reports. MTF1, encoding the yeast mitochondrial RNA polymerase specificity factor,is located on chromosome XIII

MTF1 is a nuclear gene that encodes the promoter recognition factor of the yeast mitochondrial RNA polymerase. The MTF1 gene was physically mapped to chromosome XIII. Genetic mapping data indicate that the gene is closely linked to RNA1.     

II. Yeast sequencing reports. The sequence of 12·5 kb from the right arm of chromosome II predicts a new N-terminal sequence for the IRA1 protein and reveals two new genes,one of which is a DEAD-box helicase

We have determined the complete nucleotide sequence of a 12·5 kb segment from the right arm of chromosome II carried by the cosmid α20. The sequence encodes the 5′ end of the IRA1 gene. Two complete new open reading frames and the 3′ non-coding region of the SUP1 (SUP45) gene. A comparison of our sequence with the data bank reveals a 154 amino acid extension at the N-terminus of Ira1p compared to the previously predicted sequence. According to the 11th edition of the Saccharomyces cerevisiae genetic map, our sequence should encode the MAK5 gene, which is necessary for the maintenance of dsRNA killer plasmids. One of the two new open reading frames, YBR1119, is predicted to encode an RNA helicase, thus YBR1119 may correspond to the MAK5 gene. The sequence has been deposited in the EMBL data library under Accession Number X78937.     

XI. Yeast sequencing reports. The complete sequence of an 18,002 bp segment of Saccharomyces cerevisiae chromosome XI contains the HBS1, MRP-L20 and PRP16 genes,and six new open reading frames

We report the sequence of an 18,002 bp DNA fragment from the right arm of Saccharomyces cerevisiae chromosome XI. This segment contains nine complete open reading frames (ORFs), YKR401 to YKR409, and part of another ORF, YKR400, covering altogether 87·2% of the entire sequence. One of them, YKR400, encodes an NAD-dependent 5,10-methylene-tetrahydrofolate dehydrogenase. YKR404, YKR405 and YKR406 correspond to the previously characterized HBS1, MRP-L20 and PRP16 genes, coding for a translation elongation factor, a mitochondrial ribosomal protein and an ATP-binding protein, respectively. The putative product of YKR407 contains the zinc-binding region signature of neutral zinc metallopeptidases. The five other ORFs do not show significant homology to any known protein. The sequence data reported here have been assigned EMBL accession number Z27116.     

Recovery of gene function by gene duplication in Saccharomyces cerevisiae

A prototroph revertant (Rev9) selected from an ATCase^? mutant of the URA2 gene containing three nonsense mutations was shown to contain two ATCase coding sequences. We cloned both ATCase coding areas to show that the duplicated locus (dl9) was the only functional one. Its size corresponded roughly to the second half of the URA2 wild-type gene. Sequence analysis of the 5′ end of dl9 indicated that this duplicated sequence was inserted within the intergenic region close to the MRS3 gene and was transcribed from an unknown promoter divergently from the MRS3 gene. The event leading to the revertant strain Rev9 included a rearrangement that increased the size of chromosome X by about 60 kb. In agreement with such a rearrangement, recombination was undetectable in the vicinity of the locus dl9. Genetic mapping confirms that the MRS3 gene is 2 cM distal to the URA2 gene on the right arm of chromosome X.