Substrate Specificity

Publication Title: 
Zhongguo Yi Xue Ke Xue Yuan Xue Bao. Acta Academiae Medicinae Sinicae

The silent information regulator protein 2 (Sir2) and its homologues play an important role in the regulation of cellular physiological processes such as survival, apoptosis, and aging. SIRT1, the mammalian Sir 2 homologue, has been shown to deacetylate a wide range of non-histone substrates and histone substrates. It has been constantly reported that SIRT1 may be associated with the occurrence of metabolic syndrome, genomic homeostasis, tumors, and neurodegenerative diseases.

Author(s): 
Chen, Hou-zao
Zhang, Zhu-qin
Wei, Yu-sheng
Liu, De-pei
Publication Title: 
Annual Review of Biochemistry
Author(s): 
Blackburn, E. H.
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: 
The EMBO journal

Telomerase is a reverse transcriptase minimally composed of a reverse transcriptase protein subunit and an internal RNA component that contains the templating region. Point mutations of template RNA bases can cause loss of enzymatic activity, reduced processivity and misincorporation in vitro. Here we report the first complete replacement of the nine base TETRAHYMENA: thermophila telomerase templating region in vivo with non-telomeric sequences. Rather than ablating telomerase activity, three such replaced telomerases (U9, AUN and AU4) were effective in polymerization in vitro.

Author(s): 
Ware, T. L.
Wang, H.
Blackburn, E. H.
Publication Title: 
The EMBO journal

Previous molecular genetic studies have shown that during programmed chromosomal healing, telomerase adds telomeric repeats directly to non-telomeric sequences in Tetrahymena, forming de novo telomeres. However, the biochemical mechanism underlying this process is not well understood. Here, we show for the first time that telomerase activity is capable in vitro of efficiently elongating completely non-telomeric DNA oligonucleotide primers, consisting of natural telomere-adjacent or random sequences, at low primer concentrations.

Author(s): 
Wang, H.
Blackburn, E. H.
Publication Title: 
Annual Review of Biochemistry
Author(s): 
Blackburn, E. H.
Publication Title: 
Molecular and Cellular Biology

The ribonucleoprotein enzyme telomerase synthesizes one strand of telomeric DNA by copying a template sequence within the RNA moiety of the enzyme. Kinetic studies of this polymerization reaction were used to analyze the mechanism and properties of the telomerase from Tetrahymena thermophila. This enzyme synthesizes TTGGGG repeats, the telomeric DNA sequence of this species, by elongating a DNA primer whose 3' end base pairs with the template-forming domain of the RNA.

Author(s): 
Lee, M. S.
Blackburn, E. H.
Publication Title: 
Molecular and Cellular Biology

The ribonucleoprotein enzyme telomerase synthesizes one strand of telomeric DNA by copying a template sequence within the RNA moiety of the enzyme. Kinetic studies of this polymerization reaction were used to analyze the mechanism and properties of the telomerase from Tetrahymena thermophila. This enzyme synthesizes TTGGGG repeats, the telomeric DNA sequence of this species, by elongating a DNA primer whose 3' end base pairs with the template-forming domain of the RNA.

Author(s): 
Lee, M. S.
Blackburn, E. H.
Publication Title: 
The EMBO journal

The P-glycoprotein homolog of the human malaria parasite Plasmodium falciparum (Pgh-1) has been implicated in decreased susceptibility to several antimalarial drugs, including quinine, mefloquine and artemisinin. Pgh-1 mainly resides within the parasite's food vacuolar membrane. Here, we describe a surrogate assay for Pgh-1 function based on the subcellular distribution of Fluo-4 acetoxymethylester and its free fluorochrome. We identified two distinct Fluo-4 staining phenotypes: preferential staining of the food vacuole versus a more diffuse staining of the entire parasite.

Author(s): 
Rohrbach, Petra
Sanchez, Cecilia P.
Hayton, Karen
Friedrich, Oliver
Patel, Jigar
Sidhu, Amar Bir Singh
Ferdig, Michael T.
Fidock, David A.
Lanzer, Michael
Publication Title: 
Proceedings of the National Academy of Sciences of the United States of America

With >1 million deaths annually, mostly among children in sub-Saharan Africa, malaria poses one of the most critical challenges in medicine today. Although introduction of the artemisinin class of antimalarial drugs has offered a temporary solution to the problem of drug resistance, new antimalarial drugs are needed to ensure effective control of the disease in the future. Herein, we have investigated members of the methionine aminopeptidase family as potential antimalarial targets.

Author(s): 
Chen, Xiaochun
Chong, Curtis R.
Shi, Lirong
Yoshimoto, Tadashi
Sullivan, David J.
Liu, Jun O.

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