The presence of chimeric DNA consisting of 5' regions of the hemoglobin and nucleosome assembly protein-1 genes in Paramecium caudatum macronuclear genomic DNA.
We detected an unexpected small-sized DNA fragment during polymerase chain reaction (PCR) analysis of the heterogeneity of a macronuclear intergenic region of Paramecium caudatum. Southern blotting of total genomic DNA with the PCR product as a probe indicated that the small-sized DNA fragment constituted part of the macronuclear genome. Sequencing revealed that the PCR product was a chimeric DNA structure that may be generated by tail-to-tail fusion of the 5' region of the hemoglobin (hb) gene to most of the nucleosome assembly protein-1 (nap-1) gene. Short tandem repeats consisting of tetra- and tri-nucleotides exist at the putative cleavage sites in the hb and nap-1 genes, respectively. This feature differs from those found at the boundaries of TA-internal eliminated sequences in the P. aurelia complex and at transposable elements in other species. This suggests that the chimeric DNA is generated by a novel mechanism. Although the chimeric DNA contains the hb and nap-1 promoters, transcripts corresponding to the chimeric DNA were not detected by reverse transcription (RT)-PCR analysis during vegetative cell growth. Possible roles of chimeric DNA are discussed.
Department of Biological Science, Faculty of Science, Shizuoka University, Shizuoka, Japan.
Norihito
N
Nishiyama
Kazuyuki
K
Mikami
Takehiko
T
Ochiai
Kiyoshi
K
Yamauchi
D000818:Animals; D001483:Base Sequence; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D016054:DNA, Protozoan / Q000235:genetics*; D005786:Gene Expression Regulation / Q000502:physiology; D018503:Genome, Protozoan; D006454:Hemoglobins / Q000235:genetics*; D048648:Macronucleus / Q000235:genetics; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D056490:Nucleosome Assembly Protein 1; D048488:Paramecium caudatum / Q000235:genetics* / Q000378:metabolism
D018797:Cell Cycle Proteins; D016054:DNA, Protozoan; D006454:Hemoglobins; D009687:Nuclear Proteins; D056490:Nucleosome Assembly Protein 1