Despite having high-resolution structures for eukaryotic large ribosomal subunits, it remained unclear how these ribonucleoprotein complexes are constructed in living cells. Nevertheless, knowing where ribosomal proteins interact with ribosomal RNA (rRNA) provides a strategic platform to investigate the connection between spatial and temporal aspects of 60S subunit biogenesis. We previously found that the function of individual yeast large subunit ribosomal proteins (RPLs) in precursor rRNA (pre-rRNA) processing correlates with their location in the structure of mature 60S subunits. This observation suggested that there is an order by which 60S subunits are formed. To test this model, we used proteomic approaches to assay changes in the levels of ribosomal proteins and assembly factors in preribosomes when RPLs functioning in early, middle, and late steps of pre-60S assembly are depleted. Our results demonstrate that structural domains of eukaryotic 60S ribosomal subunits are formed in a hierarchical fashion. Assembly begins at the convex solvent side, followed by the polypeptide exit tunnel, the intersubunit side, and finally the central protuberance. This model provides an initial paradigm for the sequential assembly of eukaryotic 60S subunits. Our results reveal striking differences and similarities between assembly of bacterial and eukaryotic large ribosomal subunits, providing insights into how these RNA-protein particles evolved.
"The production of ribosomes is one of the most energyconsuming processes in eukaryotic cells. Ribosome biogenesis is a highly organized and regulated pathway that requires the sequential action of >200 nonribosomal factors (Gamalinda et al. 2014). Ribosome biogenesis starts by the transcription of a pre-RNA precursor in the nucleolus , a specialized non-membrane-bound nuclear compartment . "
[Show abstract][Hide abstract] ABSTRACT: Previous work from our lab suggests that a group of interdependent assembly factors (A3 factors) is necessary to create early, stable preribosomes. Many of these proteins bind at or near internal transcribed spacer
2 (ITS2), but in their absence, ITS1 is not removed from rRNA, suggesting long-range communication between these two spacers.
By comparing the nonessential assembly factors Nop12 and Pwp1, we show that misfolding of rRNA is sufficient to perturb early
steps of biogenesis, but it is the lack of A3 factors that results in turnover of early preribosomes. Deletion of NOP12 significantly inhibits 27SA3 pre-rRNA processing, even though the A3 factors are present in preribosomes. Furthermore, pre-rRNAs are stable, indicating that the block in processing is not sufficient
to trigger turnover. This is in contrast to the absence of Pwp1, in which the A3 factors are not present and pre-rRNAs are unstable. In vivo RNA structure probing revealed that the pre-rRNA processing defects are due to misfolding of 5.8S rRNA. In the absence of
Nop12 and Pwp1, rRNA helix 5 is not stably formed. Interestingly, the absence of Nop12 results in the formation of an alternative
yet unproductive helix 5 when cells are grown at low temperatures.
[Show abstract][Hide abstract] ABSTRACT: Extensive use of wireless sensor networks for various applications like surveillance, habitat monitoring, battlefield etc., demand high probability of coverage and connectivity. The first issue deals with how well the sensor network will be able to detect the event by the sensor nodes and secondly, how efficiently the information will be communicated to the gateway node. In many applications, sensors are deployed randomly and their coverage and connectivity plays vital role in characterizing the network behavior. Modeling the randomly deployed sensor network needs heuristics, which is best studied by means of probability distributions. In this paper two algorithms i.e., grid and disc based for area based coverage are used using three deployment distributions and their performance is evaluated. Once full coverage is achieved, then ad hoc on-demand distance vector (AODV) associated clustering for grid based and ID based AODV for disc based connectivity algorithms are run on top of it to transfer the information to gateway node.
2014 International Conference on Communication Systems and Network Technologies (CSNT); 04/2014
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