The Drosophila gene abstrakt, required for visual system development, encodes a putative RNA helicase of the DEAD box protein family.

The molecular mechanisms underlying axonal pathfinding are not well understood. In a genetic screen for mutations affecting the projection of the larval optic nerve we isolated the abstrakt locus. abstrakt is required for pathfinding of the larval optic nerve, and it also affects development in both the adult visual system and the embryonic CNS. Here we report the molecular characterization of abstrakt. It encodes a putative ATP-dependent RNA helicase of the DEAD box protein family, with two rare substitutions in the PTRELA and the RG-D motifs, thought to be involved in oligonucleotide binding: serine for threonine, and lysine for arginine, respectively. Two mutant alleles of abstrakt show amino acid exchanges in highly conserved positions. A glycine to serine exchange in the HRIGR motif, which is involved in RNA binding and ATP hydrolysis, results in a complete loss of protein function; and a proline to leucine exchange located between the highly conserved ATPase A and PTRELA motifs results in temperature-sensitive protein function. Both the broad requirement for abstrakt gene function and its ubiquitous expression are consistent with a molecular function of the abstrakt protein in mRNA splicing or translational control.

Perineural invasion and seminal vesicle involvement predict pelvic lymph node metastasis in men with localized carcinoma of the prostate.

PURPOSE: We evaluate the contribution of perineural invasion and seminal vesicle biopsy results in predicting pelvic lymph node metastases in men with T1 or T2 adenocarcinoma of the prostate. MATERIALS AND METHODS: A total of 212 men with localized prostate cancer were evaluated for serum prostate specific antigen (PSA), clinical stage, Gleason score and the presence of perineural invasion. Each patient had undergone seminal vesicle biopsies and a laparoscopic pelvic lymph node dissection before definitive therapy. The pretreatment prognostic values, presence of perineural invasion and seminal vesicle involvement were compared to the results of the laparoscopic pelvic lymph node dissection. Differences in proportions were tested using the Pearson chi-square test. The effect of multiple variables was tested using a stepwise logistic regression analysis. RESULTS: PSA ranged from 1.6 to 190 ng./ml. (median 11), and 52% of patients had Gleason score 7 or greater and 67.5% had clinical stage T2b or greater disease. Of the 212 patients 37 (17.5%) had perineural invasion, 43 (20.3%) seminal vesicle involvement and 21 (10%) positive node dissections. A PSA greater than 20 ng./ml. (20 versus 6.8%, p = 0.006), Gleason score 7 or greater (15.5 versus 3.9%, p = 0.005), clinical stage T2b or greater (14 versus 0.6%, p = 0.004), presence of perineural invasion (27 versus 6%, p = 0.0001) and seminal vesicle involvement (32.6 versus 4.1%, p <0.0001) influenced nodal findings. However, in the logistic regression model only the positive seminal vesicle biopsy (p = 0.0006), presence of perineural invasion (p = 0.04) and PSA greater than 20 ng./ml. (p = 0.044) were significant variables. Of the 21 men with positive node dissections 18 (85.7%) had a positive seminal vesicle biopsy or perineural invasion. Separation of patients into a high risk group defined by a positive seminal vesicle biopsy or perineural invasion, or a low risk group defined as the absence of these features yielded a significant association with nodal involvement (28 versus 2%, p <0.0001). A separate analysis of the patients with a negative seminal vesicle biopsy demonstrated that only perineural invasion (19 versus 2%, p = 0.0002) and PSA greater than 20 ng./ml. (12 versus 2%, p = 0.01) conferred a greater risk of nodal metastases. A logistic regression analysis in the negative seminal vesicle biopsy group discarded all of the variables other than perineural invasion as significant. CONCLUSIONS: A positive seminal vesicle biopsy is the most significant predictor of pelvic lymph node metastases in men with T1 or T2 prostate cancer. Perineural invasion is also an independent predictor of nodal disease. Patients with either of these features should undergo pelvic lymph node dissection before receiving definitive therapy.

Cyclin-dependent protein kinase and cyclin homologs SSN3 and SSN8 contribute to transcriptional control in yeast.

The SSN3 and SSN8 genes of Saccharomyces cerevisiae were identified by mutations that suppress a defect in SNF1, a protein kinase required for release from glucose repression. Mutations in SSN3 and SSN8 also act synergistically with a mutation of the MIG1 repressor protein to relieve glucose repression. We have cloned the SSN3 and SSN8 genes. SSN3 encodes a cyclin-dependent protein kinase (cdk) homolog and is identical to UME5. SSN8 encodes a cyclin homolog 35% identical to human cyclin C. SSN3 and SSN8 fusion proteins interact in the two-hybrid system and coimmunoprecipitate from yeast cell extracts. Using an immune complex assay, we detected protein kinase activity that depends on both SSN3 and SSN8. Thus, the two SSN proteins are likely to function as a cdk-cyclin pair. Genetic analysis indicates that the SSN3-SSN8 complex contributes to transcriptional repression of diversely regulated genes and also affects induction of the GAL1 promoter.

Molecular analysis of the SNF8 gene of Saccharomyces cerevisiae.

Mutations in the SNF8 gene impair derepression of the SUC2 gene, encoding invertase, in response to glucose limitation of Saccharomyces cerevisiae. We report here the cloning of the SNF8 gene by complementation. Sequence analysis predicts a 26,936-dalton product. Disruption of the chromosomal locus caused a five-fold decrease in invertase derepression, defective growth on raffinose, and a sporulation defect in homozygous diploids. Genetic analysis of the interactions of the snf8 null mutation with spt6/ssn20 and ssn6 suppressors distinguished SNF8 from the groups, SNF1, SNF4 and SNF2, SNF5, SNF6. Notably, the snf8 ssn6 double mutants were extremely sick. Mutations of SNF8 and SNF7 showed similar phenotypes and genetic interactions, and the double mutant combination caused no additional phenotypic impairment. These findings suggest that SNF7 and SNF8 are functionally related.