Pdd1p, a novel chromodomain-containing protein, links heterochromatin assembly and DNA elimination in Tetrahymena.
During Tetrahymena conjugation, programmed DNA degradation occurs in two separate nuclei. Thousands of germline-specific deletion elements are removed from the genome of the developing somatic macronucleus, and the old parental macronucleus is degraded by an apoptotic mechanism. An abundant polypeptide, Pdd1p (formerly p65), localizes to both of these nuclei at the time of DNA degradation. Here we report that, in developing macronuclei, Pdd1p localizes to electron-dense, heterochromatic structures that contain germline-specific deletion elements. Pdd1p also associates with parental macronuclei during terminal stages of apoptosis. Sequencing of the PDD1 gene reveals it to be a member of the chromodomain family, suggesting a molecular link between heterochromatin assembly and programmed DNA degradation.
Madireddi
M T
MT
Department of Biology, University of Rochester, New York 14627, USA.
Coyne
R S
RS
Smothers
J F
JF
Mickey
K M
KM
Yao
M C
MC
Allis
C D
CD
D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis / Q000235:genetics; D002467:Cell Nucleus / Q000737:chemistry; D003001:Cloning, Molecular; D003227:Conjugation, Genetic / Q000502:physiology; D016054:DNA, Protozoan / Q000235:genetics* / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D017125:Genes, Protozoan / Q000235:genetics*; D005854:Germ Cells; D006570:Heterochromatin / Q000737:chemistry / Q000378:metabolism*; D048631:Micronucleus, Germline / Q000737:chemistry; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000032:analysis / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D010750:Phosphoproteins / Q000032:analysis / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D014176:Protein Biosynthesis; D015800:Protozoan Proteins; D017421:Sequence Analysis; D017422:Sequence Analysis, DNA; D017384:Sequence Deletion; D016808:Tetrahymena thermophila / Q000166:cytology / Q000235:genetics* / Q000254:growth & development
D016054:DNA, Protozoan; D006570:Heterochromatin; D009687:Nuclear Proteins; C101880:Pdd1 protein, Tetrahymena; D010750:Phosphoproteins; D015800:Protozoan Proteins