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Elucidating the molecular mechanism of LARP1 in post-transcriptional regulation of TOP transcripts

Lahr, Roni (2019) Elucidating the molecular mechanism of LARP1 in post-transcriptional regulation of TOP transcripts. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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At the heart of cell growth and proliferation is the ribosome, a multi-subunit RNA and protein ribozyme. Generating the translation machinery is a costly and highly regulated process that ensures that protein production meets the demands of the cell. Metazoan ribosomal proteins are encoded by a class of messages that ensure that each of the 80 ribosomal proteins is generated in a precise temporal and stoichiometric manner. Coordinating this is a cis-regulatory RNA motif, the 5’-Terminal Oligo-Pyrimidine (5’TOP) motif located at the very 5’ of these transcripts, which are characterized by an invariant cytosine nucleotide following the 7-methylguanosine cap. The translation of TOP transcripts is synchronized by the nutrient-sensing mTORC1 kinase complex. In unfavorable growth conditions, mTORC1 represses unwarranted ribosome biogenesis by suppressing the translation these messages.
Recently emerging as a missing link between mTOR signaling and TOP translation, La-related protein-1 (LARP1) is a downstream substrate of mTORC1 and regulator of TOP translation. The mechanism by which LARP1 represses TOP translation, however, remained unknown. We utilized complimentary biochemical and structural approaches to decipher the role of LARP1 in TOP RNA metabolism. In the first study, we identify the conserved C-terminal DM15 region of LARP1 as a novel 5’TOP RNA-binding fold. In the second study, we expand upon the molecular mechanism of LARP1 and its role in regulating mRNA metabolism. These experiments reveal that the DM15 utilizes a common protein-interaction fold to select for the invariant m7G and +1C of the 5’TOP motif. In vitro, DM15 binding occludes cap-association by translation initiation factors eIF4E and eIF4G. These data reveal the DM15 of LARP1 as a TOP-selective cap-binding protein and suggest a molecular mechanism behind LARP1-regulation of TOP mRNAs.
Current research into the role of LARP1 in translation regulation has produced conflicting results in LARP1 RNA-binding preferences and the ultimate consequence of its actions on mRNA metabolism. The data laid forth by these studies provide insight into these models and suggest a molecular mechanism for TOP mRNA recognition by DM15. The next step in LARP1 research must integrate these insights and reconcile the differing models of mRNA regulation by LARP1.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Lahr, Ronirml40@pitt.edurml40
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairBerman, Andreaajb190@pitt.eduajb190
Committee MemberSchwacha,
Committee MemberPipas,
Committee MemberVanDemark,
Committee MemberMcManus,
Date: 30 January 2019
Date Type: Publication
Defense Date: 26 July 2018
Approval Date: 30 January 2019
Submission Date: 6 December 2018
Access Restriction: 5 year -- Restrict access to University of Pittsburgh for a period of 5 years.
Number of Pages: 119
Institution: University of Pittsburgh
Schools and Programs: Dietrich School of Arts and Sciences > Biological Sciences
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: LARP, RNA-binding protein, DM15, 7-methylguanosine, TOP, Translation regulation
Date Deposited: 30 Jan 2019 23:19
Last Modified: 30 Jan 2024 06:15


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