Circular intronic RNAs(ci RNAs) escaping from DBR1 debranching of intron lariats are co-transcriptionally produced from prem RNA splicing, but their turnover and mechanism of action have remained elusive. We report th...Circular intronic RNAs(ci RNAs) escaping from DBR1 debranching of intron lariats are co-transcriptionally produced from prem RNA splicing, but their turnover and mechanism of action have remained elusive. We report that RNase H1 degrades a subgroup of ci RNAs in human cells. Many ci RNAs contain high GC% and tend to form DNA:RNA hybrids(R-loops) for RNase H1 cleavage, a process that appears to promote Pol II transcriptional elongation at ci RNA-producing loci. One ci RNA, ciankrd52, shows a stronger ability of R-loop formation than that of its cognate pre-m RNA by maintaining a locally open RNA structure in vitro. This allows the release of pre-m RNA from R-loops by ci-ankrd52 replacement and subsequent ci RNA removal via RNase H1 for efficient transcriptional elongation. We propose that such an R-loop dependent ci RNA degradation likely represents a mechanism that on one hand limits ci RNA accumulation by recruiting RNase H1 and on the other hand resolves Rloops for transcriptional elongation at some GC-rich ci RNA-producing loci.展开更多
Circular RNAs(circRNAs)are a recently dis-covered type of non‐coding RNA derived from pre‐mRNAs.R‐loops consist of a DNA:RNA hybrid andthe associated single‐stranded DNA.InArabi-dopsis thaliana,circRNA:DNA R‐loop...Circular RNAs(circRNAs)are a recently dis-covered type of non‐coding RNA derived from pre‐mRNAs.R‐loops consist of a DNA:RNA hybrid andthe associated single‐stranded DNA.InArabi-dopsis thaliana,circRNA:DNA R‐loops regulatealternative splicing(AS)ofSEPALLATA3(SEP3).However,the occurrence and functions ofcircRNAs and R‐loops inPopulus trichocarpaarelargely unexplored.Here,we performed circRNA‐enriched sequencing in the stem‐differentiatingxylem(SDX)ofP.trichocarpaand identified 2,742distinct circRNAs,including circ‐CESA4,circ‐IRX7,and circ‐GUX1,which are generated from genesinvolved in cellulose,and hemicellulose biosyn-thesis,respectively.To investigate the roles ofcircRNAs in modulating alternative splicing(AS),we detected 7,836 AS events using PacBio Iso‐Seq and identified 634 circRNAs that overlappedwith 699 AS events.Furthermore,using DNA:RNAhybrid immunoprecipitation followed by se-quencing(DRIP‐seq),we identified 8,932 R‐looppeaks that overlapped with 181 circRNAs and 672AS events.Notably,several SDX‐related circRNAsoverlapped with R‐loop peaks,pointing to theirpossible roles in modulating AS in SDX.Indeed,overexpressing circ‐IRX7increased the levels ofR‐loop structures and decreased the frequency ofintron retention in linearIRX7transcripts.Thisstudy provides a valuable R‐loop atlas resourceand uncovers the interplay between circRNAs andAS in SDX ofP.trichocarpa.展开更多
Calculations of the ElectroMagnetic(EM) response produced by a large horizontal loop placed over layered medium are rather complex because its integral expression contains the product of two Bessel functions and has a...Calculations of the ElectroMagnetic(EM) response produced by a large horizontal loop placed over layered medium are rather complex because its integral expression contains the product of two Bessel functions and has a divergent term. In this paper, an improved fast Hankel and Gaver-Stehfest transforms are introduced to solve the strong-oscillation and slow-decay properties of the integrand, where one Bessel function in the product is substituted by a carefully chosen polynomial of high accuracy and the other used as the digital filter coefficients in the convolution integral. Comparisons prove the validity and the efficiency of the proposed method.展开更多
基金This work was supported by the National Natural Science Foundation of China(NSFC)(91940303,31725009)the HHMI International Program(55008728)to L.-L.C.+2 种基金NSFC(31730111,31925011)to L.Y.Young Elite Scientists Sponsorship Program(2020QNRC001)to X.L.L.-L.C.the support from the XPLORER PRIZE.
文摘Circular intronic RNAs(ci RNAs) escaping from DBR1 debranching of intron lariats are co-transcriptionally produced from prem RNA splicing, but their turnover and mechanism of action have remained elusive. We report that RNase H1 degrades a subgroup of ci RNAs in human cells. Many ci RNAs contain high GC% and tend to form DNA:RNA hybrids(R-loops) for RNase H1 cleavage, a process that appears to promote Pol II transcriptional elongation at ci RNA-producing loci. One ci RNA, ciankrd52, shows a stronger ability of R-loop formation than that of its cognate pre-m RNA by maintaining a locally open RNA structure in vitro. This allows the release of pre-m RNA from R-loops by ci-ankrd52 replacement and subsequent ci RNA removal via RNase H1 for efficient transcriptional elongation. We propose that such an R-loop dependent ci RNA degradation likely represents a mechanism that on one hand limits ci RNA accumulation by recruiting RNase H1 and on the other hand resolves Rloops for transcriptional elongation at some GC-rich ci RNA-producing loci.
基金supported by the National Key R&D Programof China(2016YFD0600106).
文摘Circular RNAs(circRNAs)are a recently dis-covered type of non‐coding RNA derived from pre‐mRNAs.R‐loops consist of a DNA:RNA hybrid andthe associated single‐stranded DNA.InArabi-dopsis thaliana,circRNA:DNA R‐loops regulatealternative splicing(AS)ofSEPALLATA3(SEP3).However,the occurrence and functions ofcircRNAs and R‐loops inPopulus trichocarpaarelargely unexplored.Here,we performed circRNA‐enriched sequencing in the stem‐differentiatingxylem(SDX)ofP.trichocarpaand identified 2,742distinct circRNAs,including circ‐CESA4,circ‐IRX7,and circ‐GUX1,which are generated from genesinvolved in cellulose,and hemicellulose biosyn-thesis,respectively.To investigate the roles ofcircRNAs in modulating alternative splicing(AS),we detected 7,836 AS events using PacBio Iso‐Seq and identified 634 circRNAs that overlappedwith 699 AS events.Furthermore,using DNA:RNAhybrid immunoprecipitation followed by se-quencing(DRIP‐seq),we identified 8,932 R‐looppeaks that overlapped with 181 circRNAs and 672AS events.Notably,several SDX‐related circRNAsoverlapped with R‐loop peaks,pointing to theirpossible roles in modulating AS in SDX.Indeed,overexpressing circ‐IRX7increased the levels ofR‐loop structures and decreased the frequency ofintron retention in linearIRX7transcripts.Thisstudy provides a valuable R‐loop atlas resourceand uncovers the interplay between circRNAs andAS in SDX ofP.trichocarpa.
基金Supported by Chinese Government SinoProbe Plan(No.SinoProbe-09-02)R&D of Key Instruments and Technologies for Deep Resources Prospecting(No.ZDYZ 2012-1-03)
文摘Calculations of the ElectroMagnetic(EM) response produced by a large horizontal loop placed over layered medium are rather complex because its integral expression contains the product of two Bessel functions and has a divergent term. In this paper, an improved fast Hankel and Gaver-Stehfest transforms are introduced to solve the strong-oscillation and slow-decay properties of the integrand, where one Bessel function in the product is substituted by a carefully chosen polynomial of high accuracy and the other used as the digital filter coefficients in the convolution integral. Comparisons prove the validity and the efficiency of the proposed method.
