Get loop sequence from miRBase

[Palgrave]

Does anyone know a way to extract the loop sequence from the miRNA hairpin. Basically I need to extract the part that is between the 3p- and 5p part of the hairpin.

[dpryan]

Just align the 5p and 3p sequences to the hairpin sequence and take the bit between them.

[Palgrave]

Just align the 5p and 3p sequences to the hairpin sequence and take the bit between them.

I have tried, but struggle to find a command that works.

[dpryan]

I would expect that either biopython or bioperl should make this relatively straight forward. The idea is to either use base python string matching or the pairwise2 module and global alignment.

[peterawe]

Here is another suggestion using R/Bioconductor. Good luck!

require(rtracklayer)
require(BSgenome.Hsapiens.UCSC.hg19)
require(ShortRead)

mirTrack = import('ftp://mirbase.org/pub/mirbase/20/genomes/hsa.gff3')

# split into hairpin, 5arm and 3arm
hp = mirTrack[mirTrack$type != "miRNA"]
arm5 = mirTrack[grepl("-5p", mirTrack$Name)]
arm3 = mirTrack[grepl("-3p", mirTrack$Name)]

# make key for matching hairpin with arm5 and arm3
hp$arm5 = match(hp$ID, arm5$Derives_from)
hp$arm3 = match(hp$ID, arm3$Derives_from)

# discard hairpins lacking annotated 5p and 3p arms (loops not defined)
hp = hp[!is.na(hp$arm3) & !is.na(hp$arm5)]

# prepare 
hp$loopStart = 0
hp$loopEnd = 0

# miRNAs on pos and neg strand have to be parsed separately
## posStrand
isPos = as.vector(strand(hp) =="+")
hp$loopStart[isPos] = end(arm5[hp$arm5[isPos]])
hp$loopEnd[isPos] = start(arm3[hp$arm3[isPos]])

## negStrand
hp$loopEnd[!isPos] = start(arm5[hp$arm5[!isPos]])
hp$loopStart[!isPos] = end(arm3[hp$arm3[!isPos]])

# GRanges for miRNA loops
loops = GRanges(seqnames = seqnames(hp), 
  IRanges(hp$loopStart, hp$loopEnd),strand = strand(hp), 
  MI = hp$ID, Name = hp$Name)

# sanity check
hist(width(loops))

# we don't want the first/last nt of bounding mature miRs
loops = loops-1
loops$seq = getSeq(Hsapiens, loops) 
loops

# export as fastaFile
loopsFasta = loops$seq
names(loopsFasta) = paste("loopSeq", loops$MI, loops$Name, sep = "_")
writeFasta(loopsFasta, file = "mirbase20loops.fa")

[peterawe]

Hi! Here is a suggestion using R/Bioconductor. Good luck

require(rtracklayer)
require(BSgenome.Hsapiens.UCSC.hg19)
require(ShortRead)
mirTrack = import('ftp://mirbase.org/pub/mirbase/20/genomes/hsa.gff3')

# split into hairpin, 5arm and 3arm
hp = mirTrack[mirTrack$type != "miRNA"]
arm5 = mirTrack[grepl("-5p", mirTrack$Name)]
arm3 = mirTrack[grepl("-3p", mirTrack$Name)]

# make key for matching hairpin with arm5 and arm3
hp$arm5 = match(hp$ID, arm5$Derives_from)
hp$arm3 = match(hp$ID, arm3$Derives_from)

# discard hairpins without annotated 5p and 3p arms
hp = hp[!is.na(hp$arm3) & !is.na(hp$arm5)]

# prepare
hp$loopStart = 0
hp$loopEnd = 0

# miRNAs on pos and neg strand have to be parsed separately
## posStrand
isPos = as.vector(strand(hp) =="+")
hp$loopStart[isPos] = end(arm5[hp$arm5[isPos]])
hp$loopEnd[isPos] = start(arm3[hp$arm3[isPos]])
## negStrand
hp$loopEnd[!isPos] = start(arm5[hp$arm5[!isPos]])
hp$loopStart[!isPos] = end(arm3[hp$arm3[!isPos]])
# GRanges for miRNA loops
loops = GRanges(seqnames = seqnames(hp),
IRanges(hp$loopStart, hp$loopEnd),strand = strand(hp),
MI = hp$ID, Name = hp$Name)
# sanity check
hist(width(loops), breaks = 50)
# we dont want th efirst/last nt of bounding mature miRs
loops = loops-1
loops$seq = getSeq(Hsapiens, loops)
# export
loops
loopsFasta = loops$seq
names(loopsFasta) = paste("loop", loops$MI, loops$Name, sep = "_")
writeFasta(loopsFasta, file = "mirbase20loops.fa")
readLines("mirbase20loops.fa")