Molecular characterization of the D surface protein gene subfamily in Paramecium primaurelia.
When paramecium primaurelia expresses the D serotype, a major high molecular weight mRNA species is detected in the cytoplasm. Using the cDNA derived from this mRNA as a probe, three very similar genes, D alpha, D beta and D gamma, were cloned. Of these three genes, we show that only the D alpha mRNA is present in the cytoplasm of cells expressing the D serotype and corresponds to the major mRNA species. The nucleotide sequence of the entire coding region of the D alpha gene, as well as the upstream and downstream sequences, has been determined. The 7632-nucleotide open reading frame encodes a putative protein that displays the characteristic cysteine residue periodicity of Paramecium surface antigens but does not contain central tandemly repeated sequences. Partial sequences of the two nonexpressed genes D beta and D gamma indicate a high percentage of identity (90%-95%) with the D alpha gene, suggesting that D beta and D gamma genes are either very similar surface protein genes whose transcription is repressed trough mutual exclusion, or perhaps are pseudogenes. A region of variable DNA rearrangement was identified 1 kb upstream of the D gamma gene. This macronuclear region arises from the same micronuclear locus by alternative excision of internal eliminated sequences during macronuclear development.
Bourgain-Guglielmetti
F M
FM
Laboratoire de Génétique Moléculaire, Ecole Normale Supérieure, Paris, France.
Caron
F M
FM
D000595:Amino Acid Sequence; D000818:Animals; D000953:Antigens, Protozoan / Q000235:genetics*; D000954:Antigens, Surface / Q000235:genetics*; D001483:Base Sequence; D003001:Cloning, Molecular; D015342:DNA Probes; D015870:Gene Expression; D015321:Gene Rearrangement; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides; D010247:Paramecium / Q000276:immunology*
D000953:Antigens, Protozoan; D000954:Antigens, Surface; D015342:DNA Probes; D009838:Oligodeoxyribonucleotides