Lsm Proteins Are Required for Normal Processing and Stability of Ribosomal RNAs

Wellcome Trust Centre for Cell Biology, Swann Building, King's Buildings, University of Edinburgh, United Kingdom.
Journal of Biological Chemistry (Impact Factor: 4.57). 02/2003; 278(4):2147-56. DOI: 10.1074/jbc.M208856200
Source: PubMed


Depletion of any of the essential Lsm proteins, Lsm2-5p or Lsm8p, delayed pre-rRNA processing and led to the accumulation of many aberrant processing intermediates, indicating that an Lsm complex is required to maintain the normally strict order of processing events. In addition, high levels of degradation products derived from both precursors and mature rRNAs accumulated in Lsm-depleted strains. Depletion of the essential Lsm proteins reduced the apparent processivity of both 5' and 3' exonuclease activities involved in 5.8S rRNA processing, and the degradation intermediates that accumulated were consistent with inefficient 5' and 3' degradation. Many, but not all, pre-rRNA species could be coprecipitated with tagged Lsm3p, but not with tagged Lsm1p or non-tagged control strains, suggesting their direct interaction with an Lsm2-8p complex. We propose that Lsm proteins facilitate RNA protein interactions and structural changes required during ribosomal subunit assembly.

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    • "Notably, the expression of 14 genes containing a LSM (Like Sm) domain was repressed. LSM proteins form part of specific small nuclear ribonucleoproteins and are thought to be important modulators of RNA biogenesis and function [35]. The most important cellular functions induced include those associated with C-compound and carbohydrate metabolism, including metabolism of energy reserves, endocytosis and vacuolar proteolysis (Table 1). "
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    • "In concurrence with previous observations from several groups [13,48,49] most of the down-regulated genes code for ribosomal proteins and elongation factors. There were also genes coding for LSM (like-Sm) domain containing and RNA recognition motif proteins that are known for their involvement in pre-mRNA processing [50,51]. "
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    • "A difference was however noted in that at the late time point of depletion of 22 h, the DKH core and G207A mutations (Fig. 2A, lanes 9,18, respectively ) accumulated a novel RNA that extended from site D to B 2 (data not shown). The D-B 2 RNA was previously reported in strains genetically depleted for Sm-like proteins and is indicative of alterations in pre-rRNA processing kinetics (Kufel et al. 2003). "
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