Department of Chemistry and Biochemistry and the Molecular Biology Institute; University of California; Los Angeles, CA USA.
RNA Biol. 2013 Mar;10(3):353-9. doi: 10.4161/rna.23608. Epub 2013 Jan 17.
Genuine La and La-related proteins group 7 (LARP7) bind to the non-coding RNAs transcribed by RNA polymerase III (RNAPIII), which end in UUU-3'OH. The La motif and RRM1 of these proteins (the La module) cooperate to bind the UUU-3'OH, protecting the RNA from degradation, while other domains may be important for RNA folding or other functions. Among the RNAPIII transcripts is ciliate telomerase RNA (TER). p65, a member of the LARP7 family, is an integral Tetrahymena thermophila telomerase holoenzyme protein required for TER biogenesis and telomerase RNP assembly. p65, together with TER and telomerase reverse transcriptase (TERT), form the Tetrahymena telomerase RNP catalytic core. p65 has an N-terminal domain followed by a La module and a C-terminal domain, which binds to the TER stem 4. We recently showed that the p65 C-terminal domain harbors a cryptic, atypical RRM, which uses a unique mode of single- and double-strand RNA binding and is required for telomerase RNP catalytic core assembly. This domain, which we named xRRM, appears to be present in and unique to genuine La and LARP7 proteins. Here we review the structure of the xRRM, discuss how this domain could recognize diverse substrates of La and LARP7 proteins and discuss the functional implications of the xRRM as an RNP chaperone.
真核 La 和 La 相关蛋白 7 （LARP7）与 RNA 聚合酶 III （RNAPIII）转录的非编码 RNA 结合，这些 RNA 在 UUU-3'OH 处终止。这些蛋白的 La 基序和 RRM1（La 模块）共同结合 UUU-3'OH，保护 RNA 免受降解，而其他结构域可能对 RNA 折叠或其他功能很重要。在 RNAPIII 转录物中包括纤毛端粒酶 RNA（TER）。p65 是 LARP7 家族的成员，是四膜虫端粒酶全酶蛋白的必需成分，对于 TER 生物发生和端粒酶 RNP 组装很重要。p65 与 TER 和端粒酶逆转录酶（TERT）一起形成四膜虫端粒酶 RNP 催化核心。p65 具有一个 N 端结构域，随后是 La 模块和 C 端结构域，该结构域与 TER 茎 4 结合。我们最近表明，p65 C 端结构域具有一个隐匿的、非典型的 RRM，它使用独特的单链和双链 RNA 结合模式，是端粒酶 RNP 催化核心组装所必需的。这个我们命名为 xRRM 的结构域似乎存在于真正的 La 和 LARP7 蛋白中，并且是独特的。本文回顾了 xRRM 的结构，讨论了该结构域如何识别 La 和 LARP7 蛋白的各种底物，并讨论了 xRRM 作为 RNP 伴侣的功能意义。
