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Alternative 3' UTRs act as scaffolds to regulate membrane protein localization.

Berkovits BD, Mayr C - Nature (2015)

Bottom Line: This facilitates interaction of SET with the newly translated cytoplasmic domains of CD47 and results in subsequent translocation of CD47 to the plasma membrane via activated RAC1 (ref. 5).Thus, ApA contributes to the functional diversity of the proteome without changing the amino acid sequence. 3' UTR-dependent protein localization has the potential to be a widespread trafficking mechanism for membrane proteins because HuR binds to thousands of mRNAs, and we show that the long 3' UTRs of CD44, ITGA1 and TNFRSF13C, which are bound by HuR, increase surface protein expression compared to their corresponding short 3' UTRs.We propose that during translation the scaffold function of 3' UTRs facilitates binding of proteins to nascent proteins to direct their transport or function--and this role of 3' UTRs can be regulated by ApA.

View Article: PubMed Central - PubMed

Affiliation: Cancer Biology and Genetics Program, Memorial Sloan Kettering Cancer Center, 1275 York Ave, New York, New York 10065, USA.

ABSTRACT
About half of human genes use alternative cleavage and polyadenylation (ApA) to generate messenger RNA transcripts that differ in the length of their 3' untranslated regions (3' UTRs) while producing the same protein. Here we show in human cell lines that alternative 3' UTRs differentially regulate the localization of membrane proteins. The long 3' UTR of CD47 enables efficient cell surface expression of CD47 protein, whereas the short 3' UTR primarily localizes CD47 protein to the endoplasmic reticulum. CD47 protein localization occurs post-translationally and independently of RNA localization. In our model of 3' UTR-dependent protein localization, the long 3' UTR of CD47 acts as a scaffold to recruit a protein complex containing the RNA-binding protein HuR (also known as ELAVL1) and SET to the site of translation. This facilitates interaction of SET with the newly translated cytoplasmic domains of CD47 and results in subsequent translocation of CD47 to the plasma membrane via activated RAC1 (ref. 5). We also show that CD47 protein has different functions depending on whether it was generated by the short or long 3' UTR isoforms. Thus, ApA contributes to the functional diversity of the proteome without changing the amino acid sequence. 3' UTR-dependent protein localization has the potential to be a widespread trafficking mechanism for membrane proteins because HuR binds to thousands of mRNAs, and we show that the long 3' UTRs of CD44, ITGA1 and TNFRSF13C, which are bound by HuR, increase surface protein expression compared to their corresponding short 3' UTRs. We propose that during translation the scaffold function of 3' UTRs facilitates binding of proteins to nascent proteins to direct their transport or function--and this role of 3' UTRs can be regulated by ApA.

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3'UTR isoforms that encode proteins using UDPL contain uridine-rich elementsShown are the 3'UTR sequences of CD47, CD44, HuR-BS and HuR-BSΔ. Red, ApA signals. Blue, uridine-rich elements with the potential to be HuR-binding sites.
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Figure 7: 3'UTR isoforms that encode proteins using UDPL contain uridine-rich elementsShown are the 3'UTR sequences of CD47, CD44, HuR-BS and HuR-BSΔ. Red, ApA signals. Blue, uridine-rich elements with the potential to be HuR-binding sites.

Mentions: To determine if UDPL is a more widespread phenomenon, we examined the localization of four additional transmembrane proteins which are derived from mRNAs with 3'UTR isoforms that can be bound by HuR 6–8 (Extended Data Fig. 3, 4). TSPAN13 has only one 3'UTR isoform, whereas the other three genes [CD44, ITGA1, TNFRSF13C (encoding BAFF receptor, BAFFR)] use ApA to generate alternative 3'UTR isoforms (Fig. 2c and Extended Data Fig. 2a, f) 3. As was the case for CD47, KD of HuR decreased surface expression of all four proteins without changing total protein levels (Fig. 2c and Extended Data Fig. 2f). As was done for CD47, we generated GFP-fused LU and SU constructs for CD44, ITGA1, and TNFRSF13C with their respective TMDs, C-termini and 3'UTRs. For all tested genes, the longer 3'UTR increased surface localization of GFP-TM (Fig. 1f–h, 2d and Extended Data Fig. 2g). This demonstrates that UDPL has the potential to be a widespread phenomenon.


Alternative 3' UTRs act as scaffolds to regulate membrane protein localization.

Berkovits BD, Mayr C - Nature (2015)

3'UTR isoforms that encode proteins using UDPL contain uridine-rich elementsShown are the 3'UTR sequences of CD47, CD44, HuR-BS and HuR-BSΔ. Red, ApA signals. Blue, uridine-rich elements with the potential to be HuR-binding sites.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4697748&req=5

Figure 7: 3'UTR isoforms that encode proteins using UDPL contain uridine-rich elementsShown are the 3'UTR sequences of CD47, CD44, HuR-BS and HuR-BSΔ. Red, ApA signals. Blue, uridine-rich elements with the potential to be HuR-binding sites.
Mentions: To determine if UDPL is a more widespread phenomenon, we examined the localization of four additional transmembrane proteins which are derived from mRNAs with 3'UTR isoforms that can be bound by HuR 6–8 (Extended Data Fig. 3, 4). TSPAN13 has only one 3'UTR isoform, whereas the other three genes [CD44, ITGA1, TNFRSF13C (encoding BAFF receptor, BAFFR)] use ApA to generate alternative 3'UTR isoforms (Fig. 2c and Extended Data Fig. 2a, f) 3. As was the case for CD47, KD of HuR decreased surface expression of all four proteins without changing total protein levels (Fig. 2c and Extended Data Fig. 2f). As was done for CD47, we generated GFP-fused LU and SU constructs for CD44, ITGA1, and TNFRSF13C with their respective TMDs, C-termini and 3'UTRs. For all tested genes, the longer 3'UTR increased surface localization of GFP-TM (Fig. 1f–h, 2d and Extended Data Fig. 2g). This demonstrates that UDPL has the potential to be a widespread phenomenon.

Bottom Line: This facilitates interaction of SET with the newly translated cytoplasmic domains of CD47 and results in subsequent translocation of CD47 to the plasma membrane via activated RAC1 (ref. 5).Thus, ApA contributes to the functional diversity of the proteome without changing the amino acid sequence. 3' UTR-dependent protein localization has the potential to be a widespread trafficking mechanism for membrane proteins because HuR binds to thousands of mRNAs, and we show that the long 3' UTRs of CD44, ITGA1 and TNFRSF13C, which are bound by HuR, increase surface protein expression compared to their corresponding short 3' UTRs.We propose that during translation the scaffold function of 3' UTRs facilitates binding of proteins to nascent proteins to direct their transport or function--and this role of 3' UTRs can be regulated by ApA.

View Article: PubMed Central - PubMed

Affiliation: Cancer Biology and Genetics Program, Memorial Sloan Kettering Cancer Center, 1275 York Ave, New York, New York 10065, USA.

ABSTRACT
About half of human genes use alternative cleavage and polyadenylation (ApA) to generate messenger RNA transcripts that differ in the length of their 3' untranslated regions (3' UTRs) while producing the same protein. Here we show in human cell lines that alternative 3' UTRs differentially regulate the localization of membrane proteins. The long 3' UTR of CD47 enables efficient cell surface expression of CD47 protein, whereas the short 3' UTR primarily localizes CD47 protein to the endoplasmic reticulum. CD47 protein localization occurs post-translationally and independently of RNA localization. In our model of 3' UTR-dependent protein localization, the long 3' UTR of CD47 acts as a scaffold to recruit a protein complex containing the RNA-binding protein HuR (also known as ELAVL1) and SET to the site of translation. This facilitates interaction of SET with the newly translated cytoplasmic domains of CD47 and results in subsequent translocation of CD47 to the plasma membrane via activated RAC1 (ref. 5). We also show that CD47 protein has different functions depending on whether it was generated by the short or long 3' UTR isoforms. Thus, ApA contributes to the functional diversity of the proteome without changing the amino acid sequence. 3' UTR-dependent protein localization has the potential to be a widespread trafficking mechanism for membrane proteins because HuR binds to thousands of mRNAs, and we show that the long 3' UTRs of CD44, ITGA1 and TNFRSF13C, which are bound by HuR, increase surface protein expression compared to their corresponding short 3' UTRs. We propose that during translation the scaffold function of 3' UTRs facilitates binding of proteins to nascent proteins to direct their transport or function--and this role of 3' UTRs can be regulated by ApA.

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