extracting sequence from a genome
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@iain-gallagher-2532
Last seen 9.3 years ago
United Kingdom
Hello List I have a dataframe of miRNA genomic positions and I would like to get sequence for 200bp upstream of each microRNA. library(BSgenome.Rnorvegicus.UCSC.rn4)# get genome ftpAddr <- "ftp://mirbase.org/pub/mirbase/CURRENT/genomes/rno.gff" # get miR coords mirInfo <- read.table(ftpAddr) # as dataframe seqs <- list() # holder for (i in 1:nrow(mirInfo)){ seq <- getSeq(Rnorvegicus, paste('chr', mirInfo[i,1], sep=''), start = mirInfo[i,4], end = mirInfo[i,4]+200) seqs <- c(seqs, seq) } This works but seems to be pretty inefficient in terms of computing power as my pc locks up during the loop. Could someone point me to a better way? Thanks iain
miRNA microRNA miRNA microRNA • 6.2k views
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Tim Triche ★ 4.2k
@tim-triche-3561
Last seen 4.2 years ago
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what you want to do is create a Ranges object and then get a View of the sequences. library(Biostrings) library(GenomicRanges) mirs <- GRanges( paste('chr', mirInfo[i,1], sep=''), IRanges(start=mirInfo[i,4], width=1), strand=whereverYouKeepTheStrand ) upstream <- flank(mirs, 200) upseqs <- Views(Rnorvegicus, mirs) show(upseqs) Untested because I am lazy as hell, but it should work, and be a LOT faster. On Thu, Mar 15, 2012 at 8:23 AM, Iain Gallagher < iaingallagher@btopenworld.com> wrote: > > > Hello List > > I have a dataframe of miRNA genomic positions and I would like to get > sequence for 200bp upstream of each microRNA. > > library(BSgenome.Rnorvegicus.UCSC.rn4)# get genome > > ftpAddr <- "ftp://mirbase.org/pub/mirbase/CURRENT/genomes/rno.gff" # get > miR coords > mirInfo <- read.table(ftpAddr) # as dataframe > > seqs <- list() # holder > > for (i in 1:nrow(mirInfo)){ > seq <- getSeq(Rnorvegicus, paste('chr', mirInfo[i,1], sep=''), start = > mirInfo[i,4], end = mirInfo[i,4]+200) > seqs <- c(seqs, seq) > } > > This works but seems to be pretty inefficient in terms of computing power > as my pc locks up during the loop. > > Could someone point me to a better way? > > Thanks > > iain > > _______________________________________________ > Bioconductor mailing list > Bioconductor@r-project.org > https://stat.ethz.ch/mailman/listinfo/bioconductor > Search the archives: > http://news.gmane.org/gmane.science.biology.informatics.conductor > -- *A model is a lie that helps you see the truth.* * * Howard Skipper<http: cancerres.aacrjournals.org="" content="" 31="" 9="" 1173.full.pdf=""> [[alternative HTML version deleted]]
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Howdy, On Thu, Mar 15, 2012 at 1:10 PM, Tim Triche, Jr. <tim.triche at="" gmail.com=""> wrote: > what you want to do is create a Ranges object and then get a View of the > sequences. > > > library(Biostrings) > library(GenomicRanges) > mirs <- GRanges( paste('chr', mirInfo[i,1], sep=''), > ? ? ? ? ? ? ? ? IRanges(start=mirInfo[i,4], width=1), > ? ? ? ? ? ? ? ? strand=whereverYouKeepTheStrand ) > upstream <- flank(mirs, 200) > upseqs <- Views(Rnorvegicus, mirs) > show(upseqs) > > Untested because I am lazy as hell, but it should work, and be a LOT faster. Maybe in R 2.16 ... R> Views(Hsapiens, GRanges(c('chr1', 'chr2'), IRanges(c(6e6, 6e6), width=10), '+')) Error in function (classes, fdef, mtable) : unable to find an inherited method for function "Views", for signature "BSgenome" ;-) -steve -- Steve Lianoglou Graduate Student: Computational Systems Biology ?| Memorial Sloan-Kettering Cancer Center ?| Weill Medical College of Cornell University Contact Info: http://cbio.mskcc.org/~lianos/contact
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Yeah I just realized that when I pasted it in to execute it. Trying to find where exactly I did this in the past (because it worked back then) On Thu, Mar 15, 2012 at 10:42 AM, Steve Lianoglou < mailinglist.honeypot@gmail.com> wrote: > Howdy, > > On Thu, Mar 15, 2012 at 1:10 PM, Tim Triche, Jr. <tim.triche@gmail.com> > wrote: > > what you want to do is create a Ranges object and then get a View of the > > sequences. > > > > > > library(Biostrings) > > library(GenomicRanges) > > mirs <- GRanges( paste('chr', mirInfo[i,1], sep=''), > > IRanges(start=mirInfo[i,4], width=1), > > strand=whereverYouKeepTheStrand ) > > upstream <- flank(mirs, 200) > > upseqs <- Views(Rnorvegicus, mirs) > > show(upseqs) > > > > Untested because I am lazy as hell, but it should work, and be a LOT > faster. > > Maybe in R 2.16 ... > > R> Views(Hsapiens, GRanges(c('chr1', 'chr2'), IRanges(c(6e6, 6e6), > width=10), '+')) > Error in function (classes, fdef, mtable) : > unable to find an inherited method for function "Views", for > signature "BSgenome" > > ;-) > > -steve > > -- > Steve Lianoglou > Graduate Student: Computational Systems Biology > | Memorial Sloan-Kettering Cancer Center > | Weill Medical College of Cornell University > Contact Info: http://cbio.mskcc.org/~lianos/contact > -- *A model is a lie that helps you see the truth.* * * Howard Skipper<http: cancerres.aacrjournals.org="" content="" 31="" 9="" 1173.full.pdf=""> [[alternative HTML version deleted]]
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Hi Gentlemen Thanks for taking the time. Here's where I am just now: library(BSgenome.Rnorvegicus.UCSC.rn4)# get genome library(GenomicRanges) fl <- "ftp://mirbase.org/pub/mirbase/CURRENT/genomes/rno.gff" # get miR coords gff <- read.table(fl) # as dataframe names <- gff[,10] nms <- gsub(";", "", gsub("\"", "", gsub("ID=\"", "", names))) # a set of nested gsub with regex to leave only the text in the double quotes gr <- GRanges(seqnames = Rle(paste('chr', gff[,1], sep='')), ranges = IRanges(gff[,4], end = gff[,5], names = nms), strand = Rle(gff[,7])) seqs <- getSeq(Rnorvegicus, flank(gr, 200)) names(seqs) <- nms It's much lighter on it's feet than a loop and a nice intro to the GenomicRanges package for me. As a follow-up question I'm going to write out the seqs object as fasta and use it in clover for TFBS analysis. I was wondering whether the strand is taken into account when I get the flanking sequence i.e. is the sequence returned from the + or - strand as defined in the GRanges object? I only ask this because presumably that will affect my TFBS analysis and if so I might want to reverse / complement all those sequences that are upstream of miRs transcribed from the - strand. Best iain ________________________________ From: "Tim Triche, Jr." <tim.triche@gmail.com> To: Steve Lianoglou <mailinglist.honeypot at="" gmail.com=""> Cc: Iain Gallagher <iaingallagher at="" btopenworld.com="">; bioconductor <bioconductor at="" stat.math.ethz.ch=""> Sent: Thursday, 15 March 2012, 17:44 Subject: Re: [BioC] extracting sequence from a genome Yeah I just realized that when I pasted it in to execute it. ?Trying to find where exactly I did this in the past (because it worked back then) On Thu, Mar 15, 2012 at 10:42 AM, Steve Lianoglou <mailinglist.honeypot at="" gmail.com=""> wrote: Howdy, > > >On Thu, Mar 15, 2012 at 1:10 PM, Tim Triche, Jr. <tim.triche at="" gmail.com=""> wrote: >> what you want to do is create a Ranges object and then get a View of the >> sequences. >> >> >> library(Biostrings) >> library(GenomicRanges) >> mirs <- GRanges( paste('chr', mirInfo[i,1], sep=''), >> ? ? ? ? ? ? ? ? IRanges(start=mirInfo[i,4], width=1), >> ? ? ? ? ? ? ? ? strand=whereverYouKeepTheStrand ) >> upstream <- flank(mirs, 200) >> upseqs <- Views(Rnorvegicus, mirs) >> show(upseqs) >> >> Untested because I am lazy as hell, but it should work, and be a LOT faster. > >Maybe in R 2.16 ... > >R> Views(Hsapiens, GRanges(c('chr1', 'chr2'), IRanges(c(6e6, 6e6), >width=10), '+')) >Error in function (classes, fdef, mtable) ?: >?unable to find an inherited method for function "Views", for >signature "BSgenome" > >;-) > >-steve > >-- >Steve Lianoglou >Graduate Student: Computational Systems Biology >?| Memorial Sloan-Kettering Cancer Center >?| Weill Medical College of Cornell University >Contact Info: http://cbio.mskcc.org/~lianos/contact > -- A model is a lie that helps you see the truth. Howard Skipper
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Hi Iain, On Thu, Mar 15, 2012 at 2:16 PM, Iain Gallagher <iaingallagher at="" btopenworld.com=""> wrote: > > > Hi Gentlemen > > Thanks for taking the time. Here's where I am just now: > > library(BSgenome.Rnorvegicus.UCSC.rn4)# get genome > library(GenomicRanges) > > fl <- "ftp://mirbase.org/pub/mirbase/CURRENT/genomes/rno.gff" # get miR coords > gff <- read.table(fl) # as dataframe > > names <- gff[,10] > nms <- gsub(";", "", gsub("\"", "", gsub("ID=\"", "", names))) # a set of nested gsub with regex to leave only the text in the double quotes > > gr <- GRanges(seqnames = Rle(paste('chr', gff[,1], sep='')), ranges = IRanges(gff[,4], end = gff[,5], names = nms), strand = Rle(gff[,7])) > > seqs <- getSeq(Rnorvegicus, flank(gr, 200)) > names(seqs) <- nms > > It's much lighter on it's feet than a loop and a nice intro to the GenomicRanges package for me. > > As a follow-up question I'm going to write out the seqs object as fasta and use it in clover for TFBS analysis. > > > I was wondering whether the strand is taken into account when I get the flanking sequence i.e. is the sequence returned from the + or - strand as defined in the GRanges object? A call to `flank` on a GRanges object is "strand aware" -- is that what you're asking? Consider: R> gr <- GRanges('chr1', IRanges(c(20, 20), width=5), c('+', '-')) R> flank(gr, 10) GRanges with 2 ranges and 0 elementMetadata values: seqnames ranges strand <rle> <iranges> <rle> [1] chr1 [10, 19] + [2] chr1 [25, 34] - R> flank(gr, 10, start=FALSE) GRanges with 2 ranges and 0 elementMetadata values: seqnames ranges strand <rle> <iranges> <rle> [1] chr1 [25, 34] + [2] chr1 [10, 19] - getSeq is also strand aware -- it will return the reverse complement of the sequence in your bounds if its on the `-` strand. HTH, -steve -- Steve Lianoglou Graduate Student: Computational Systems Biology ?| Memorial Sloan-Kettering Cancer Center ?| Weill Medical College of Cornell University Contact Info: http://cbio.mskcc.org/~lianos/contact
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