Ciliophora

Publication Title: 
Science (New York, N.Y.)

The RNA moiety of the ribonucleoprotein enzyme telomerase from the ciliate Euplotes crassus was identified and its gene was sequenced. Functional analysis, in which oligonucleotides complementary to portions of the telomerase RNA were tested for their ability to prime telomerase in vitro, showed that the sequence 5' CAAAACCCCAAA 3' in this RNA is the template for synthesis of telomeric TTTTGGGG repeats by the Euplotes telomerase. The data provide a direct demonstration of a template function for a telomerase RNA and demarcate the outer boundaries of the telomeric template.

Author(s): 
Shippen-Lentz, D.
Blackburn, E. H.
Publication Title: 
Cold Spring Harbor Symposia on Quantitative Biology
Author(s): 
Blackburn, E. H.
Budarf, M. L.
Challoner, P. B.
Cherry, J. M.
Howard, E. A.
Katzen, A. L.
Pan, W. C.
Ryan, T.
Publication Title: 
Annual Review of Biochemistry
Author(s): 
Blackburn, E. H.
Publication Title: 
Cell

Macronuclear DNA from the protozoan G. chattoni, a holotrichous ciliate, was analyzed. Most, if not all, of the macronuclear DNA is subchromosomal, ranging in size from above 100 kb down to 2.1 kb, with molecules in the lower molecular weight range being resolvable by gel electrophoresis into reproducible, specific, discrete size classes. A prominent class of linear 9.3 kb molecules consists of single free rRNA genes. Upon denaturation of total macronuclear DNA was found as single-stranded circles.

Author(s): 
Katzen, A. L.
Cann, G. M.
Blackburn, E. H.
Publication Title: 
Nucleic Acids Research

We have analyzed the nucleotide sequences of the nontranscribed spacer (NTS) and transcription initiation and termination regions of the extrachromosomal rDNAs of the ciliated protozoans Tetrahymena thermophila and Glaucoma chattoni. The sequences surrounding the sites of transcription initiation and termination are highly conserved. The only extensive homologies of the NTS regions occur in five sets of dispersed repetitive sequences.

Author(s): 
Challoner, P. B.
Amin, A. A.
Pearlman, R. E.
Blackburn, E. H.
Publication Title: 
Nucleic Acids Research

We sequenced and compared the telomeric regions of linear rDNAs from vegetative macronuclei of several ciliates in the suborder Tetrahymenina. All telomeres consisted of tandemly repeated C4A2 sequences, including the 5' telomere of the 11 kb rDNA from developing macronuclei of Tetrahymena thermophila. Our sequence of the 11 kb 5' telomeric region shows that each one of a previously described pair of inverted repeats flanking the micronuclear rDNA (Yao et al., Mol. Cell. Biol.

Author(s): 
Challoner, P. B.
Blackburn, E. H.
Publication Title: 
Annual Review of Genetics
Author(s): 
Blackburn, E. H.
Karrer, K. M.
Publication Title: 
Molecular and Cellular Biology

A telomere terminal transferase activity was identified in developing macronuclear extracts from Euplotes crassus. The activity was essentially unregulated in vitro: up to 50 tandem repeats of the Euplotes telomeric repeat sequence TTTTGGGG were added onto synthetic telomeric oligonucleotide primers. Both the structure of the telomere substrate and its 3'-terminal sequence were recognized. The activity was destroyed by low concentrations of RNase A.

Author(s): 
Shippen-Lentz, D.
Blackburn, E. H.
Publication Title: 
Nucleic Acids Research

We have analyzed the nucleotide sequences of the nontranscribed spacer (NTS) and transcription initiation and termination regions of the extrachromosomal rDNAs of the ciliated protozoans Tetrahymena thermophila and Glaucoma chattoni. The sequences surrounding the sites of transcription initiation and termination are highly conserved. The only extensive homologies of the NTS regions occur in five sets of dispersed repetitive sequences.

Author(s): 
Challoner, P. B.
Amin, A. A.
Pearlman, R. E.
Blackburn, E. H.
Publication Title: 
Cell

The RNA moiety of the ribonucleoprotein enzyme telomerase contains the template for telomeric DNA synthesis. We present a secondary structure model for telomerase RNA, derived by a phylogenetic comparative analysis of telomerase RNAs from seven tetrahymenine ciliates. The telomerase RNA genes from Tetrahymena malaccensis, T. pyriformis, T. hyperangularis, T. pigmentosa, T. hegewishii, and Glaucoma chattoni were cloned, sequenced, and compared with the previously cloned RNA gene from T. thermophila and with each other.

Author(s): 
Romero, D. P.
Blackburn, E. H.

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