Molecular cloning and cell-cycle-dependent expression of a novel NIMA (never-in-mitosis in Aspergillus nidulans)-related protein kinase (TpNrk) in Tetrahymena cells.
With the intention of investigating the signal-transduction pathway that mediates the cold-stress response in Tetrahymena, we isolated a gene that encodes a novel protein kinase of 561 amino acids, termed Tetrahymena pyriformis NIMA (never-in-mitosis in Aspergillus nidulans)-related protein kinase (TpNrk), by differential display from Tetrahymena cells exposed to temperature shift-down. TpNrk possesses an N-terminal protein kinase domain that is highly homologous with other NIMA-related protein kinases (Neks) involved in the control of the cell cycle. The TpNrk protein is 42% identical in its catalytic domain with human Nek2, 41% identical with mouse Nek1 and 37% with A. nidulans NIMA. In addition, TpNrk and these NIMA-related kinases have long, basic C-terminal extensions and are therefore similar in overall structure. In order to further explore the function of the TpNrk gene and the association of the cold stress with the cell cycle of Tetrahymena, changes of TpNrk mRNA were determined during the course of the synchronous cell division induced by the intermittent heat treatment. The level of TpNrk transcription increased immediately after the end of the heat treatment, with a peak at 30 min, and declined thereafter reaching the minimum level when nearly 80% of the cells synchronously entered cell division (75 min after the end of heat treatment). The accumulation of TpNrk mRNA starting from 0 min to 30 min after the end of the heat treatment was assumed to be a prerequisite for the start of synchronous cell division. These results suggest that TpNrk may have a role in the cell cycle of Tetrahymena, and that mRNA expression, at least, is under tight cell-cycle control.
Department of Biochemistry, Gifu University School of Medicine, Tsukasamachi-40, Gifu 500, Japan.
S
S
Wang
S
S
Nakashima
H
H
Sakai
O
O
Numata
K
K
Fujiu
Y
Y
Nozawa
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002453:Cell Cycle / Q000502:physiology*; D018797:Cell Cycle Proteins; D003001:Cloning, Molecular; D018076:DNA, Complementary; D015723:Gene Library; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D000072380:NIMA-Related Kinase 1; D000072379:NIMA-Related Kinases; D014176:Protein Biosynthesis; D017346:Protein Serine-Threonine Kinases / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D012333:RNA, Messenger / Q000096:biosynthesis; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry; D015183:Restriction Mapping; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013696:Temperature; D013769:Tetrahymena pyriformis / Q000166:cytology / Q000235:genetics / Q000502:physiology*; D014158:Transcription, Genetic
D018797:Cell Cycle Proteins; D018076:DNA, Complementary; D012333:RNA, Messenger; D011994:Recombinant Proteins; C000606914:NEK1 protein, human; D000072380:NIMA-Related Kinase 1; D000072379:NIMA-Related Kinases; C442331:NIMA-related kinase 6; C000606920:Nek1 protein, mouse; D017346:Protein Serine-Threonine Kinases