Microscopic characterization of a putative ER-membrane targeted Puf RNA-binding protein in Arabidopsis thaliana

Date
2014-08-05
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Abstract
Cellular messenger RNAs (mRNAs) are associated with RNA-binding proteins (RBPs) that form ribonucleoprotein (RNP) complexes. These RNP complexes are the functional units that participate in post-transcriptional gene regulation activities. One group of RBPs that plays an important role in regulating cytoplasmic post-transcriptional control is the Puf family of RNA-binding proteins. Some of the general characteristics of plant Puf proteins, including their biochemistry, systematics and cell biology, have been studied in the Muench laboratory. The research reported in this thesis was aimed at conducting a microscopic characterization of a Puf protein, APUM6 that potentially targets to the membrane of the endoplasmic reticulum (ER). The ER is an organelle that has an essential role in protein synthesis. APUM6 does not appear to possess a signal peptide that is common in ER targeted proteins. Hydrophobicity plots further indicate the presence of a weak hydrophobic region that could assist in ER-anchorage. The hypothesis of this thesis is that APUM6 anchors to the membrane of the ER and that this membrane anchorage is facilitated by a palmitoylation, a post-translational modification that attaches a palmitate to a cysteine residue in the protein to increase membrane-protein interactions. Also, it is proposed that the cytoskeleton plays an important role in the localization of APUM6. First, the subcellular localization of APUM6 was determined by expressing it as a fluorescent fusion protein in epidermal cells of fava bean and Arabidopsis using confocal laser scanning microscopy. These experiments determined that APUM6 is indeed localized to the ER membrane. Second, using cytoskeletal disrupting drugs, it was demonstrated that cytoskeleton was not involved in the localization of APUM6. Also, palmitoylation inhibitor 2-bromopalmitate treatment showed that palmitoylation likely is not mediating the anchoring of APUM6 on the ER membrane. The possible role for an ER targeted Puf protein could be to facilitate targeting of mRNAs that encode secretory or cytosolic proteins to the ER surface in order to enhance the efficiency of translation/and or import into the ER.
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Keywords
Biology--Cell, Biology--Molecular
Citation
Saha, P. (2014). Microscopic characterization of a putative ER-membrane targeted Puf RNA-binding protein in Arabidopsis thaliana (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/26909