Identification of a C-terminal Poly(A)-binding Protein (PABP)-PABP Interaction Domain

Melo, E. O.; Dhália, Rafael; de, Cezar Martins; Standart, Nancy; Neto, Osvaldo P. de Melo

doi:10.1074/jbc.m307624200

Cited by 78 publications

(48 citation statements)

References 54 publications

(102 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A tripartite complex of RNA-binding proteins assembles on the ARS to promote repression: IMP1, UNR, and PABP (49,56). Presumably the RNP complex sterically blocks 40 S ribosome scanning, but repression requires the MLLE domain of PABP, indicating that protein-protein interactions may also be important (53,57). D, Puf5p disrupts PABP-mediated translational activation, possibly by interfering with the interaction between Pab1p and eIF4G (this work).…”

Section: Discussionmentioning

confidence: 96%

A Role for the Poly(A)-binding Protein Pab1p in PUF Protein-mediated Repression

Chritton

Wickens

2011

Journal of Biological Chemistry

View full text Add to dashboard Cite

PUF proteins regulate translation and mRNA stability throughout eukaryotes. Using a cell-free translation assay, we examined the mechanisms of translational repression of PUF proteins in the budding yeast Saccharomyces cerevisiae. We demonstrate that the poly(A)-binding protein Pab1p is required for PUF-mediated translational repression for two distantly related PUF proteins: S. cerevisiae Puf5p and Caenorhabditis elegans FBF-2. Pab1p interacts with oligo(A) tracts in the HO 3-UTR, a target of Puf5p, to dramatically enhance the efficiency of Puf5p repression. Both the Pab1p ability to activate translation and interact with eukaryotic initiation factor 4G (eIF4G) were required to observe maximal repression by Puf5p. Repression was also more efficient when Pab1p was bound in close proximity to Puf5p. Puf5p may disrupt translation initiation by interfering with the interaction between Pab1p and eIF4G. Finally, we demonstrate two separable mechanisms of translational repression employed by Puf5p: a Pab1p-dependent mechanism and a Pab1p-independent mechanism.Regulation of messenger RNA (mRNA) is an important part of gene expression. Each mRNA contains instructions that determine where and when it will be expressed. Many of the instructions are contained in the untranslated regions (UTRs) 2 of the mRNA (1, 2). UTRs encode instructions for translation activation, repression, mRNA decay, or localization (3). The instructions take the form of primary sequences and structural elements that can be recognized by RNA-binding proteins (RBPs) and microRNAs (miRNAs). The combination of these factors assembled on each transcript determines the fate of each mRNA.PUF proteins are a family of RBPs that regulate the translation and stability of mRNAs to which they bind, typically by repressing their expression (4 -9). PUFs recognize elements that contain a conserved UGU sequence located in the 3Ј-UTR of target mRNAs (8, 10). PUF proteins often act as part of a larger regulatory complex, providing RNA binding specificity while other factors accomplish regulation (7,(11)(12)(13)(14).PUF proteins utilize two mechanisms to repress mRNA expression: destabilization and translational repression (8). Shortening of the poly(A) tail is the first step of mRNA decay in eukaryotes (15). In yeast, Puf5p interacts with Pop2p, a member of the Ccr4/Not deadenylase complex, facilitating deadenylation and decay of target mRNAs (11, 16). PUF-mediated recruitment of the Ccr4/Not complex has been demonstrated in Caenorhabditis elegans, Drosphila, and humans, suggesting that it is a conserved regulatory mechanism (11, 12).PUF proteins employ several different mechanisms to disrupt translation initiation. During the first step of initiation, the mRNA is circularized by the eIF4F complex, which then facilitates ribosome recruitment (17, 18). Circularization is achieved by eIF4G binding to both the cap-binding protein eIF4E and the poly(A)-binding protein PABP, bringing both ends of the mRNA in proximity (19). Drosophila Pumilio disrupts circularization by r...

show abstract

Section: Discussionmentioning

confidence: 96%

A Role for the Poly(A)-binding Protein Pab1p in PUF Protein-mediated Repression

Chritton

Wickens

2011

Journal of Biological Chemistry

View full text Add to dashboard Cite

show abstract

“…As the P domain is known to be required for interactions among higher eukaryotic PAB1 molecules (26,31), its effects on deadenylation might be occurring through a required contact among PAB1 molecules. We subsequently tested the model that the effects on the rates of deadenylation caused by deletion of certain PAB1 domains were the result of alterations in PAB1 interactions with itself.…”

Section: Vol 27 2007 Pab1 Self-association Precludes Binding To Polmentioning

confidence: 99%

“…The C region binds PAN3, which is required for PAN2 activity, eRF3, and other proteins (24,27,29). The P domain of higher eukaryotic PAB1 is responsible for PAB1-PAB1 interactions (26,31). The RRM domains of PAB1 consist of four ␤-strands that form the RNA binding surface backed by two ␣-helices (18).…”

mentioning

confidence: 99%

PAB1 Self-Association Precludes Its Binding to Poly(A), Thereby Accelerating CCR4 Deadenylation In Vivo

Yao

Chiang

Zhang

et al. 2007

Molecular and Cellular Biology

115

View full text Add to dashboard Cite

The mRNA deadenylation process, catalyzed by the CCR4 deadenylase, is known to be the major factor controlling mRNA decay rates in Saccharomyces cerevisiae. We have identified the proline-rich region and RRM1 domains of poly(A) binding protein (PAB1) as necessary for CCR4 deadenylation. Deletion of either of these regions but not other regions of PAB1 significantly reduced PAB1-PAB1 protein interactions, suggesting that PAB1 oligomerization is a required step for deadenylation. Moreover, defects in these two regions inhibited the formation of a novel, circular monomeric PAB1 species that forms in the absence of poly(A). Removal of the PAB1 RRM3 domain, which promoted PAB1 oligomerization and circularization, correspondingly accelerated CCR4 deadenylation. Circular PAB1 was unable to bind poly(A), and PAB1 multimers were severely deficient or unable to bind poly(A), implicating the PAB1 RNA binding surface as critical in making contacts that allow PAB1 self-association. These results support the model that the control of CCR4 deadenylation in vivo occurs in part through the removal of PAB1 from the poly(A) tail following its self-association into multimers and/or a circular species. Known alterations in the P domains of different PAB proteins and factors and conditions that affect PAB1 self-association would, therefore, be expected to be critical to controlling mRNA turnover in the cell.mRNA degradation is a process involving the interaction and exchange of multiple multisubunit complexes and RNA binding proteins (8). Central to mRNA degradation is the removal of the poly(A) tail (deadenylation) that is controlled by a number of proteins associating with the mRNA in a structure termed the mRNP. Principal among these factors present in the mRNP are the poly(A) binding protein (PAB1), translation initiation and termination factors, the cytoplasmic deadenylases, and the factors that bind to the mRNA and elicit alterations in the mRNA degradative rate. The processes of mRNA degradation and deadenylation and the protein complexes that are involved are highly evolutionarily conserved from Saccharomyces cerevisiae to humans.The principal pathway for mRNA degradation in yeast proceeds through several steps. First, there is an initial trimming of about 15 to 20 nucleotides (nt) of the poly(A) tail to a length of about 60 to 80 nt that is specific for each mRNA and that appears to be carried out by PAN2/PAN3, presumably a cytoplasmic process (2,19,48). This trimming requires PAB1 and the translation termination factors eRF1 and eRF3 (5, 24), and all these factors are known to associate with each other (10, 23, 24, 29). Second, the major part of deadenylation utilizes the CCR4-NOT deadenylase complex (16,48). CCR4 is the catalytic component of this complex (7, 47) and shortens the poly(A) tail of mRNA to an end point size of about 8 to 12 nt (14). Poly(A) tail shortening down to an oligo(A) form (8 to 12 A's) may lead, in turn, to the reduced ability of PAB1 to bind the poly(A) tail that may alter the translation initiation...

show abstract

“…Among the four highly conserved RNA-binding domains of PABP, the first two show specificity toward poly(A), whereas the third and fourth RNA-binding domains can also bind to poly(G) and poly(U) (13)(14)(15). The C-terminal region of PABP does not bind RNA, but can interact with other polypeptides and promotes oligomerization of PABP on poly(A) (16). The C-terminal region contains a highly conserved 74-amino acid-long PABC (for PABP C-terminal) domain that binds to the eukaryotic release factor 3 and two regulators of mRNA translation, Paip1 and Paip2 (17,18).…”

mentioning

confidence: 99%

Reduced Stability of Mitogen-activated Protein Kinase Kinase-2 mRNA and Phosphorylation of Poly(A)-binding Protein (PABP) in Cells Overexpressing PABP

Musa

Bag

2006

Journal of Biological Chemistry

View full text Add to dashboard Cite

The poly(A)-binding protein (PABP) is an important regulator of mRNA translation and stability. The cellular level of PABP is controlled by regulating its mRNA translation by a feedback mechanism. The important aspect of this mechanism is that PABP binds to an adenosine-rich cis-element at the 5-untranslated region of its own mRNA and inhibits its translation. To assess the importance of controlling the PABP level, we studied the effect of PABP overexpression on the transcription profile using the microarray technique. In PABP-overexpressing cells, 19 mRNAs showed a reduction in cellular levels due to reduced mRNA stability, and one showed an increase due to increased mRNA stability. Among these mRNAs, the MKK-2 mRNA encodes the protein kinase activator of ERK1/2 kinase, which is involved in the phosphorylation of eukaryotic initiation factor (eIF) 4E. As a result, mRNA translation may be regulated by the cellular level of MKK-2. In this study, we show that the abundance of the MKK-2 polypeptide is reduced in PABP-overexpressing cells. In these cells, the levels of phosphorylated PABP, eIF4E, and ERK2 are also reduced. Treatment of HeLa cells with the MKK-2 inhibitor U0126 reduced PABP phosphorylation, suggesting that the phosphorylation of PABP is mediated by the MKK-2/ ERK signaling pathway. Thus, a novel signaling pathway involving MKK-2 and ERK1/2 may down-regulate the activity of PABP and eIF4E by controlling their phosphorylation and compensates for the effect of excess cellular PABP.Regulation of the rate of protein synthesis is important for the control of cellular growth and differentiation. Cells respond to changes in growth conditions by fine-tuning the rate of mRNA translation. Initiation of mRNA translation is the rate-limiting step and is often regulated by controlling the interaction between the 5Ј-cap of the mRNA and several initiation factors, including eukaryotic initiation factor (eIF) 2 4E, eIF4G, and eIF4A (1). A recent study has shown that the poly(A)-binding protein (PABP) also behaves like a genuine initiation factor because depletion of PABP from a cell-free extract prevents initiation of mRNA translation (2). The 3Ј-poly(A) tail-bound PABP interacts with eIF4G and circularizes the translating mRNA. This process is believed to enhance mRNA translation by promoting recirculation of terminating ribosomal subunits from the 3Ј-end of the mRNA for another round of initiation (3-6). Although this model is widely accepted, it has not been proven to occur in vivo. In addition, if PABP is essential for mRNA translation, it is possible that PABP participates in mRNA translation by a yet unknown mechanism, as the presence of 3Ј-poly(A) (and thus circularization of mRNA) is not essential for translation initiation of capped mRNAs (7,8).PABP binds to the 3Ј-poly(A) track of eukaryotic mRNA. It also interacts with polypeptides involved in regulating the translation and stability of mRNA (9 -12). Among the four highly conserved RNA-binding domains of PABP, the first two show specificity toward poly(A),...

show abstract

Identification of a C-terminal Poly(A)-binding Protein (PABP)-PABP Interaction Domain

Cited by 78 publications

References 54 publications

A Role for the Poly(A)-binding Protein Pab1p in PUF Protein-mediated Repression

A Role for the Poly(A)-binding Protein Pab1p in PUF Protein-mediated Repression

PAB1 Self-Association Precludes Its Binding to Poly(A), Thereby Accelerating CCR4 Deadenylation In Vivo

Reduced Stability of Mitogen-activated Protein Kinase Kinase-2 mRNA and Phosphorylation of Poly(A)-binding Protein (PABP) in Cells Overexpressing PABP

Contact Info

Product

Resources

About