Nabeel-Shah S, Ashraf K, Saettone A, Garg J, Derynck J, Lambert JP, Pearlman RE, Fillingham J (2020) Nucleus-specific linker histones Hho1 and Mlh1 form distinct protein interactions during growth, starvation and development in Tetrahymena thermophila. Scientific reports 10(1):168 PUBMED:31932604
Akematsu T, Sánchez-Fernández R, Kosta F, Holzer E, Loidl J (2019) The Transmembrane Protein Semi1 Positions Gamete Nuclei for Reciprocal Fertilization in Tetrahymena. iScience 23(1):100749 PUBMED:31884169
Tian M, Loidl J (2019) An MCM family protein promotes interhomolog recombination by preventing precocious intersister repair of meiotic DSBs. PLoS genetics 15(12):e1008514 PUBMED:31815942
Identifiers and Description
Gene Model Identifier
TTHERM_00284230
Standard Name
DCL1 (DiCer-Like 1)
Aliases
PreTt04959 | 25.m00423 | 3694.m00206
Description
Dicer-related RNase III protein; one of three Dicer-like proteins described in T. thermophila; required for processing micronuclear transcripts into scnRNAs, methylation of histone H3 on IESs, and segregation of micronuclear chromosomes
( SD01814 ) Micronucleus: homozygous neo3 KO of DCL1, Macronucleus: homozygous ΔDCL1, neo 3 was deleted in mac and assorted to pm-s; MTT1-DCL1 replaced some of MTT1
( SD01815 ) Micronucleus: homozygous neo3 KO of DCL1, Macronucleus: homozygous ΔDCL1, neo 3 was deleted in mac and assorted to pm-s; MTT1-DCL1 replaced some of MTT1
( SD01925 ) Micronucleus: homozygous neo3 KO of DCL1, Macronucleus: homozygous ΔDCL1 ,neo 3 was deleted in mac and assorted to pm-s;
( SD01926 ) Micronucleus: homozygous neo3 KO of DCL1, Macronucleus: homozygous ΔDCL1 ,neo 3 was deleted in mac and assorted to pm-s
( SD01927 ) Micronucleus: homozygous neo3 KO of DCL1, Macronucleus: ΔDCL1 ,neo 3 was deleted in mac and assorted to pm-s
( SD02277 ) Micronucleus: homozygous neo3 KO of DCL1, Macronucleus: ΔDCL1 ,neo 3 was deleted in mac and assorted to pm-s
( SD02278 ) Micronucleus: homozygous neo3 KO of DCL1, Macronucleus: homozygous ΔDCL1 ,neo 3 was deleted in mac and assorted to pm-s; MTT1-DCL1 replaced some of MTT1
( SD02279 ) Micronucleus: homozygous neo3 KO of DCL1, Macronucleus: homozygous ΔDCL1 ,neo 3 was deleted in mac and assorted to pm-s; MTT1-DCL1 replaced some of MTT1
( SD02832 ) Macronucleus: Mac-DCL1 was completely replaced with DCL1-HA- with neo3 in 3’ flanking region
( SD02835 ) Micronucleus: heterozygous neo3 KO of DCL1,
( SD02836 ) Micronucleus: heterozygous neo3 KO of DCL1
( SD02589 ) Micronucleus: Neo 3 into DCL1 and HA tagged TWI11 into the TWI11 locus
( SD02590 ) Micronucleus: Neo 3 into DCL1 and HA tagged TWI11 into the TWI11 locus
( SD02591 ) Micronucleus: HA tagged TWI 11 Macronucleus: Neo3 KO of DCL1
( SD02592 ) Micronucleus: HA tagged TWI 11, heterozygous with WT Macronucleus: Neo3 KO of DCL1 complete somatic
A proposed model for the mechanism of programmed DNA elimination in Tetrahymena is based on the timing of expression, cellular distribution, mutant phenotypes, and predicted functions of the protein and RNA components involved. In this model, both strands of the micronuclear genome (or perhaps only the portions containing internal eliminated sequences) are transcribed early in conjugation to produce large non-genic, double-stranded RNAs. This transcription is likely performed by RNA Polymerase II, based on the localization of its subunit Rpb3p to the micronucleus during this time. These transcripts pass to the cytoplasm where they are processed into short (~28 nucleotide) scan RNAs (scnRNA) by the dicer-like protein Dcl1p, similar to the production of the small inhibitory RNAs (siRNA) central to the RNA interference (RNAi) pathway of other eukaryotes. The scnRNAs complex with Twi1p, a member of the PPD (PAZ and Piwi Domain) protein family, whose members are commonly involved in RNAi and related processes. The scnRNA/Twi1p complexes enter the old macronucleus, where scnRNAs homologous to DNA sequences found there are degraded. The remaining scnRNAs, comprised of micronuclear-restricted sequences, are transferred to the developing macronucleus. There, histone H3 proteins (Hht1p, Hht2p) that are bound to sections of the genome sharing identity to the scnRNAs are methylated on lysine-9. This modification, which is often associated with the formation of heterochromatin, is recognized by one or more of the chromodomains belonging to Pdd1p and Pdd3p. Regions of DNA associated with these modified histones are eliminated from the developing macronuclear genome.
Associated Literature
Ref:29021213: Noto T, Mochizuki K (2017) Whats, hows and whys of programmed DNA elimination in Tetrahymena. Open biology 7(10):
Ref:26769902: Woo TT, Chao JL, Yao MC (2016) Dynamic distributions of long double-stranded RNA in Tetrahymena during nuclear development and genome rearrangements. Journal of cell science 129(5):1046-58
Ref:16199890: Malone CD, Anderson AM, Motl JA, Rexer CH, Chalker DL (2005) Germ line transcripts are processed by a Dicer-like protein that is essential for developmentally programmed genome rearrangements of Tetrahymena thermophila. Molecular and cellular biology 25(20):9151-64
Ref:15598983: Mochizuki K, Gorovsky MA (2005) A Dicer-like protein in Tetrahymena has distinct functions in genome rearrangement, chromosome segregation, and meiotic prophase. Genes & development 19(1):77-89
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