Abstract
SINEUPs are long non-coding RNAs (lncRNAs) that contain a SINE element, and which up-regulate the translation of target mRNA. They have been studied in a wide range of applications, as both biological and therapeutic tools, although the underpinning molecular mechanism is unclear. Here, we focused on the sub-cellular distribution of target mRNAs and SINEUP RNAs, performing co-transfection of expression vectors for these transcripts into human embryonic kidney cells (HEK293T/17), to investigate the network of translational regulation. The results showed that co-localization of target mRNAs and SINEUP RNAs in the cytoplasm was a key phenomenon. We identified PTBP1 and HNRNPK as essential RNA binding proteins. These proteins contributed to SINEUP RNA sub-cellular distribution and to assembly of translational initiation complexes, leading to enhanced target mRNA translation. These findings will promote a better understanding of the mechanisms employed by regulatory RNAs implicated in efficient protein translation.
Highlights
More than 70% of the mammalian genome is transcribed into RNAs (Carninci et al, 2005; The ENCODE Project Consortium, 2012)
We demonstrated that a synthetic SINEUP RNA plays a critical role in the enhancement of the translation of its target mRNA by 1) co-localizing with the target mRNA in the cytoplasm, 2) interacting with SINEUP RNA binding proteins (RBPs) to influence the SINEUP RNA’s distribution and 3) increasing target mRNA shifting to polysome by participating in translational initiation assembly
By conducting RNA FISH, we revealed that the co-localization of enhanced green fluorescent protein (EGFP) mRNA and SINEUP-GFP RNA in the cytoplasm was required for positive translational regulation
Summary
More than 70% of the mammalian genome is transcribed into RNAs (Carninci et al, 2005; The ENCODE Project Consortium, 2012) The majority of these RNAs do not encode proteins and are called non-coding RNAs. A large fraction of non-coding RNAs are found as sense-antisense pairwise transcripts that are co-regulated at the transcription level (Katayama et al, 2005). A large fraction of non-coding RNAs are found as sense-antisense pairwise transcripts that are co-regulated at the transcription level (Katayama et al, 2005) Some of these non-coding RNAs, such as transfer RNA (tRNA) and ribosomal RNA (rRNA), have been intensely studied, the biological function of 98.5% of the long non-coding RNAs (lncRNAs), which are defined as non-coding RNAs longer than 200 nucleotides (Kapranov et al, 2007), are still unknown (de Hoon et al, 2015).
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