Identification and characterization of telomerase in plants /
Telomerase is a ribonucleoprotein enzyme with a reverse transcription activity. Telomerase uses a portion of its own RNA moiety to template the synthesis of short, guanine-rich, tandem DNA repeats. Telomeric repeats are added onto chromosomal 3' ends to compensate for the failure of conventiona...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1999.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=731686431&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Telomerase is a ribonucleoprotein enzyme with a reverse transcription activity. Telomerase uses a portion of its own RNA moiety to template the synthesis of short, guanine-rich, tandem DNA repeats. Telomeric repeats are added onto chromosomal 3' ends to compensate for the failure of conventional DNA polymerizes to completely replicate DNA ends. Telomerase also can be capable of healing broken chromosome ends by perforating de novo telomere addition. The Telomere Repeat Amplification Protocol was used to detect an activity in carrot, cauliflower, soybean, and Arabidopsis extracts with all the characteristics expected for a telomerase enzyme. Telomerase activity is abundant in cauliflower meristematic tissue and undifferentiated callus cells from Arabidopsis, soybean and carrot, but is not detectable in differentiated tissues from mature plants. The correlation between telomerase expression and cellular proliferation capacity errors the changes in human telomerase levels during differentiation and immortalization. Three distinct modes of new telomere formation by telomerase were uncovered. Soybean and carrot enzymes only elongate substrates bearing several residues of telomeric sequence. Arabidopsis and cauliflower telomerases efficiently extend non-telomeric DNA primers by positioning the 3' terminus at a default site on the enzyme's internal RNA template. Telomerases from Silene latifolia, sorghum, wheat and maize are error prone in both the initiation and elongation steps. We also investigated the causes of the developmentally programmed differences in chromosome healing capacity in maize embryo. No functional difference in de novo telomere formation by embryo and endosperm extracts was found. Thus, the high levels of telomerase activity found in the embryo appear to be sufficient for efficient chromosome healing. The Arabidopsis telomerase reverse transcription gene, AtTERT was cloned and characterized. AtTERT is predicted to encode a highly basic, 131 kDa protein harboring the reverse transcription and telomerase-specific motifs common to all TERT proteins. AtTERT mRNA is more abundant in telomerase-positive callus cells versus telomerase-negative leaf tissue. Plants homozygous for a T-DNA insertion into AtTERT lack telomerase activity and undergo telomere shortening at a rate of 500 bp per generation. This gradual loss of telomeric DNA may explain how plants grow and develop without detectable telomerase activity in their vegetative meristems. |
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| Item Description: | Vita. "Major Subject: Biochemistry". |
| Physical Description: | xi, 217 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 127-178). |