Project description:Human LIN28A and B are RNA-binding proteins (RBPs) conserved in animals with important roles during development and stem cell reprogramming. We used Photoactivatable-Ribonucleoside-Enhanced Crosslinking and Immunoprecipitation (PAR-CLIP) in HEK293 cells and identified a largely overlapping set of ~3,000 mRNAs at ~9,500 sites located in the 3M-bM-^@M-^YUTR and CDS. In vitro and in vivo, LIN28 preferentially bound single-stranded RNA containing a uridine-rich element and one or more flanking guanosines, and appeared to be able to disrupt base-pairing to access these elements when embedded in predicted secondary structure. In HEK293 cells, LIN28 protein binding mildly stabilized target mRNAs and increased protein abundance. The top targets were its own mRNAs and those of other RBPs and cell-cycle regulators. Alteration of LIN28 protein levels also negatively regulated the abundance of some, but not all let-7 miRNA family members, indicating sequence-specific binding of let-7 precursors to LIN28 proteins and competition with cytoplasmic miRNA biogenesis factors. LIN28 protein PAR-CLIP
Project description:The conserved human LIN28 RNA-binding proteins function in development, maintenance of pluripotency and oncogenesis. We used PAR-CLIP and a newly developed variant of this method, iDo-PAR-CLIP, to identify LIN28B targets as well as sites bound by the individual RNA binding domains of LIN28B in the human transcriptome at nucleotide resolution. The position of target binding sites reflected the known structural relative orientation of individual LIN28B binding domains, validating iDo-PAR-CLIP. Our data suggest that LIN28B directly interacts with most expressed mRNAs and members of the let-7 microRNA family. The Lin28 binding motif detected in pre-let-7 was enriched in mRNA sequences bound by LIN28B. Upon LIN28B knock down, cell proliferation and the cell cycle were strongly impaired. Quantitative shotgun proteomics of LIN28B depleted cells revealed significant reduction of protein synthesis from its RNA targets that function in translation, mRNA splicing and cell cycle control. Computational analyses provided evidence that the strength of protein synthesis reduction correlated with the location of LIN28B binding sites within target transcripts. We used PAR-CLIP and a newly developed variant of this method, iDo-PAR-CLIP, to identify LIN28B targets as well as sites bound by the individual RNA binding domains of LIN28B in the human transcriptome at nucleotide resolution.
Project description:Human LIN28A and B are RNA-binding proteins (RBPs) conserved in animals with important roles during development and stem cell reprogramming. We used Photoactivatable-Ribonucleoside-Enhanced Crosslinking and Immunoprecipitation (PAR-CLIP) in HEK293 cells and identified a largely overlapping set of ~3,000 mRNAs at ~9,500 sites located in the 3M-bM-^@M-^YUTR and CDS. In vitro and in vivo, LIN28 preferentially bound single-stranded RNA containing a uridine-rich element and one or more flanking guanosines, and appeared to be able to disrupt base-pairing to access these elements when embedded in predicted secondary structure. In HEK293 cells, LIN28 protein binding mildly stabilized target mRNAs and increased protein abundance. The top targets were its own mRNAs and those of other RBPs and cell-cycle regulators. Alteration of LIN28 protein levels also negatively regulated the abundance of some, but not all let-7 miRNA family members, indicating sequence-specific binding of let-7 precursors to LIN28 proteins and competition with cytoplasmic miRNA biogenesis factors. To assess whether the transcripts identified by PAR-CLIP are regulated by LIN28B we analyzed the mRNA levels of LIN28B overexpressing and LIN28B-depleted cells using microarrays. Transcripts crosslinked to LIN28B were slightly downregulated upon LIN28B knockdown compared to LIN28B overexpression indicating that LIN28B stabilizes transcripts. The RBP LIN28B was depleted by siRNAs and the expression levels was compared to mock-transfected HEK293 cells The RBP LIN28B was depleted by siRNAs and the expression levels was compared to mock-transfected HEK293 cells
Project description:Human LIN28A and B are RNA-binding proteins (RBPs) conserved in animals with important roles during development and stem cell reprogramming. We used Photoactivatable-Ribonucleoside-Enhanced Crosslinking and Immunoprecipitation (PAR-CLIP) in HEK293 cells and identified a largely overlapping set of ~3,000 mRNAs at ~9,500 sites located in the 3’UTR and CDS. In vitro and in vivo, LIN28 preferentially bound single-stranded RNA containing a uridine-rich element and one or more flanking guanosines, and appeared to be able to disrupt base-pairing to access these elements when embedded in predicted secondary structure. In HEK293 cells, LIN28 protein binding mildly stabilized target mRNAs and increased protein abundance. The top targets were its own mRNAs and those of other RBPs and cell-cycle regulators. Alteration of LIN28 protein levels also negatively regulated the abundance of some, but not all let-7 miRNA family members, indicating sequence-specific binding of let-7 precursors to LIN28 proteins and competition with cytoplasmic miRNA biogenesis factors. To assess whether the transcripts identified by PAR-CLIP are regulated by LIN28B we analyzed the mRNA levels of LIN28B overexpressing and LIN28B-depleted cells using microarrays. Transcripts crosslinked to LIN28B were slightly downregulated upon LIN28B knockdown compared to LIN28B overexpression indicating that LIN28B stabilizes transcripts. The RBP LIN28B was depleted by siRNAs and the expression levels was compared to mock-transfected HEK293 cells
Project description:Human LIN28A and B are RNA-binding proteins (RBPs) conserved in animals with important roles during development and stem cell reprogramming. We used Photoactivatable-Ribonucleoside-Enhanced Crosslinking and Immunoprecipitation (PAR-CLIP) in HEK293 cells and identified a largely overlapping set of ~3,000 mRNAs at ~9,500 sites located in the 3’UTR and CDS. In vitro and in vivo, LIN28 preferentially bound single-stranded RNA containing a uridine-rich element and one or more flanking guanosines, and appeared to be able to disrupt base-pairing to access these elements when embedded in predicted secondary structure. In HEK293 cells, LIN28 protein binding mildly stabilized target mRNAs and increased protein abundance. The top targets were its own mRNAs and those of other RBPs and cell-cycle regulators. Alteration of LIN28 protein levels also negatively regulated the abundance of some, but not all let-7 miRNA family members, indicating sequence-specific binding of let-7 precursors to LIN28 proteins and competition with cytoplasmic miRNA biogenesis factors.
Project description:Human LIN28A and B are RNA-binding proteins (RBPs) conserved in animals with important roles during development and stem cell reprogramming. We used Photoactivatable-Ribonucleoside-Enhanced Crosslinking and Immunoprecipitation (PAR-CLIP) in HEK293 cells and identified a largely overlapping set of ~3,000 mRNAs at ~9,500 sites located in the 3’UTR and CDS. In vitro and in vivo, LIN28 preferentially bound single-stranded RNA containing a uridine-rich element and one or more flanking guanosines, and appeared to be able to disrupt base-pairing to access these elements when embedded in predicted secondary structure. In HEK293 cells, LIN28 protein binding mildly stabilized target mRNAs and increased protein abundance. The top targets were its own mRNAs and those of other RBPs and cell-cycle regulators. Alteration of LIN28 protein levels also negatively regulated the abundance of some, but not all let-7 miRNA family members, indicating sequence-specific binding of let-7 precursors to LIN28 proteins and competition with cytoplasmic miRNA biogenesis factors.
Project description:The conserved human LIN28 RNA-binding proteins function in development, maintenance of pluripotency and oncogenesis. We used PAR-CLIP and a newly developed variant of this method, iDo-PAR-CLIP, to identify LIN28B targets as well as sites bound by the individual RNA binding domains of LIN28B in the human transcriptome at nucleotide resolution. The position of target binding sites reflected the known structural relative orientation of individual LIN28B binding domains, validating iDo-PAR-CLIP. Our data suggest that LIN28B directly interacts with most expressed mRNAs and members of the let-7 microRNA family. The Lin28 binding motif detected in pre-let-7 was enriched in mRNA sequences bound by LIN28B. Upon LIN28B knock down, cell proliferation and the cell cycle were strongly impaired. Quantitative shotgun proteomics of LIN28B depleted cells revealed significant reduction of protein synthesis from its RNA targets that function in translation, mRNA splicing and cell cycle control. Computational analyses provided evidence that the strength of protein synthesis reduction correlated with the location of LIN28B binding sites within target transcripts.