Title
Branchiostoma Floridae Has Separate Healing and Sealing Enzymes for 5′-phosphate RNA Ligation
Document Type
Article
Publication Date
2010
Published In
Proceedings of the National Academy of Sciences
Volume
107
Issue
39
Pages
16834-16839
DOI
10.1073/pnas.1011703107
Recommended Citation
Englert, M.; Sheppard, K.; Gundllapalli, S.; Beier, H.; Soll, D., Branchiostoma floridae has separate healing and sealing enzymes for 5'-phosphate RNA ligation. Proc Natl Acad Sci U S A 2010, 107 (39), 16834-9.
Abstract
Animal cells have two tRNA splicing pathways: (i) a 5′-P ligation mechanism, where the 5′-phosphate of the 3′ tRNA half becomes the junction phosphate of the new phosphodiester linkage, and (ii) a 3′-P ligation process, in which the 3′-phosphate of the 5′ tRNA half turns into the junction phosphate. Although both activities are known to exist in animals, in almost three decades of investigation, neither of the two RNA ligases has been identified. Here we describe a gene from the chordate Branchiostoma floridae that encodes an RNA ligase (Bf RNL) with a strict requirement for RNA substrates with a 2′-phosphate terminus for the ligation of RNAs with 5′-phosphate and 3′-hydroxyl ends. Unlike the yeast and plant tRNA ligases involved in tRNA splicing, Bf RNL lacks healing activities and requires the action of a polynucleotide kinase (PNK) and a cyclic phosphodiesterase (CDPase) in trans. The activities of these two enzymes were identified in a single B. floridae protein (Bf PNK/CPDase). The combined activities of Bf RNL and Bf PNK/CPDase are sufficient for the joining of tRNA splicing intermediates in vitro, and for the functional complementation of a tRNA ligase-deficient Saccharomyces cerevisiae strain in vivo. Hence, these two proteins constitute the 5′-P RNA ligation pathway in an animal organism.