BIOCHEMISTRY. For the article “A universal telomerase RNA core structure includes structured motifs required for binding the telomerase reverse transcriptase protein,” by Jue Lin, Hinh Ly, Arif Hussain, Mira Abraham, Sivan Pearl, Yehuda Tzfati, Tristram G. Parslow, and Elizabeth H. Blackburn, which appeared in issue 41, October 12, 2004, of Proc. Natl. Acad. Sci. USA (101, 14713-14718; first published September 15, 2004; 10.1073/pnas.0405879101), the authors note the following: “We have found an error in the Kluyveromyces lactis structure in Fig. 3. In CS1, a G residue was replaced with an A, and some of the sequence was inadvertently omitted. The complementary strand (CS4-ext) is correct, and the base pairing is still the same (with G:U instead of A:U). The correct sequence of CS1 and the pairing element are in the GenBank database (nucleotides 51-78 of the transcript): CTGGGGTGGTAAGGACCAGTGCCACACT. In addition, at the left side of the K. lactis structure a C incorrectly appeared as a G, and stem 2 should be 5′-CCAAA... UUUGG. Also, an A nucleotide is missing in the Saccharomyces cerevisiae secondary structure, and a G nucleotide was replaced by a C in human sequence.” These errors do not affect the conclusions of the article. The corrected figure and its legend appear below.
Fig. 3.
Proposed unified model for the common secondary structure core for TER RNA. (A) Comparison of the common core and TERT-binding regions in representative species of eukaryotes: the budding yeasts S. cerevisiae, K. lactis, human (vertebrate), and Tetrahymena thermophila (ciliate) TER RNAs. (B) Proposed unified model for the common secondary structure core for all TER RNAs. The model (see text) is based on data from the present article combined with published data from ciliates, mammals, and yeasts (Kluyveromyces and Saccharomyces groups). Nucleotides or structures important for binding of TERT (Est2p in S. cerevisiae) are indicated by gray shading. The barrier function of the TER RNA is achieved in different ways in different phylogenetic groups (Upper). In the budding yeasts only the secondary structure of the 5′ boundary element (helix 1) is important, with no requirement for a given sequence. Helix 1 begins one to four TER RNA residues upstream from the last nucleotide of the maximal putative template (15, 16). In contrast, in ciliate TERs, the 5′ boundary element is a conserved primary sequence ACUG 5′, located two residues upstream from the last template residue copied (26) (Lower). In vertebrate TERs, the P1b helix provides template 5′ boundary function (32). Like the yeast helix 1, the barrier function of vertebrate P1b helix requires only its paired structure, but not its sequence, and the P1b helix can be located four or more residues upstream of the 5′ boundary of the template used in vitro. However, in mouse, rat, and hamster TER RNAs, the 5′ end of the whole TER molecule is only 2 bases up from the 5′ boundary of the templating domain. Thus, it has been surmised that run-off copying occurs in those species, and then the extra bases are trimmed off by the inherent endonuclease activity of the TER ribonucleoprotein (32, 38, 39).