Genomic structure of two ras family genes in the slime mold Physarum polycephalum.
Genomic structure of two Physarum polycephalum ras family genes, Ppras2 and Pprap1, has been determined, including the upstream region of the latter. The genes are interrupted by three and four introns, respectively. The first intron of Ppras2 has the same location within the coding sequence as the first intron in another ras homolog from this organism, Ppras1 [Trzcińska-Danielewicz, J., Kozlowski, P., and Toczko, K. (1996). "Cloning and genomic sequence of the Physarum polycephalum Ppras1 gene, a homologue of the ras protooncogene", Gene 169, pp. 143-144]. All introns, ranging from 53 to ca. 460 base pairs, have the canonical 5' and 3' ends, are greatly enriched in pyrimidines in the coding strand and have frequent pyrimidines-only tracts. These latter features seem to be responsible for the difficulties in cloning and sequencing of parts of these genes. Short sequences shared with P. polycephalum transposon-like repeats are common in the introns, indicating a possible role of transposition in intron evolution. In all three ras family genes phase zero introns are located mostly between sequences coding for regular protein secondary structure elements.
Trzcińska-Danielewicz
Joanna
J
Institute of Biochemistry, Warsaw University, Miecznikowa 1, 02096 Warsaw, Poland.
Kozlowski
Piotr
P
Gierdal
Katarzyna
K
Wiejak
Jolanta
J
Jagielski
Adam
A
Toczko
Kazimierz
K
Fronk
Jan
J
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D016054:DNA, Protozoan / Q000032:analysis; D019143:Evolution, Molecular; D005091:Exons; D018503:Genome, Protozoan; D007438:Introns; D008969:Molecular Sequence Data; D016839:Physarum polycephalum / Q000235:genetics*; D018631:ras Proteins / Q000235:genetics*
D016054:DNA, Protozoan; D018631:ras Proteins