motifScanHits {seqPattern} | R Documentation

## Occurrence of motifs in a set of ordered sequences

### Description

Finds positions of sequence motif hits above a specified threshold in a list of sequences of the same length ordered by a provided index. Motif is specified by a position weight matrix (PWM) that contains estimated probability of base b at position i and is usually constructed via call to `PWM` function. Position of each motif hit is specified in two-dimensional matrix, i.e. the first coordinate provides the ordinal number of the sequence and the second coordinate gives the position within the sequence where the motif occurs.

### Usage

    motifScanHits(regionsSeq, motifPWM, minScore = "80%",
        seqOrder = c(1:length(regionsSeq)))

### Arguments

`regionsSeq` | A `DNAStringSet` object. Set of sequences of the same length in which to search for the motif hits.
`motifPWM` | A numeric matrix representing the Position Weight Matrix (PWM), such as returned by `PWM` function. Can contain either probabilities or log2 probability ratio of base b at position i.
`minScore` | The minimum score for counting a motif hit. Can be given as a character string containing a percentage (e.g. `"85%"`) of the PWM score or a single number specifying score threshold. If a percentage is given, it is converted to a score value taking into account both minimal and maximal possible PWM scores as follows: `minPWMscore + percThreshold/100 * (maxPWMscore - minPWMscore)` This differs from the formula in the `matchPWM` function from the `Biostrings` package which takes into account only the maximal possible PWM score and considers the given percentage as the percentage of that maximal score: `percThreshold/100 * maxPWMscore`
`seqOrder` | Integer vector specifying the order of the provided input sequences. Must have the same length as the number of sequences in the `regionSeq`. The default value will order the sequences as they are ordered in the input `regionSeq` object.

### Details

This function uses the `matchPWM` function to find matches to given motif in a set of input sequences. Only matches above specified `minScore` are considered as hits. Input sequences must all be of the same length and are ordered according to the index provided in the `seqOrder` argument, creating a `n * m` matrix, where `n` is the number of sequences and `m` is the length of the sequences. Positions of motif hits in the resulting matrix are returned as two-dimensional coordinates.

### Value

The function returns a `data.frame` with positions of the motif hits in the set of input sequences. The input sequences of the same length are sorted according to the index in `seqOrder` argument and the positions of motif hits in the resulting `n * m` matrix (where `n` is the number of sequences and `m` is the length of the sequence) are provided. The `sequence` column in the data.frame provides the ordinal number of the sequence in the ordered list of sequences and the `position` column provides the start position of the motif hit within that sequence.

### Author(s)

Vanja Haberle

### See Also

`plotMotifDensityMap`
`getPatternOccurrenceList`

### Examples

    library(GenomicRanges)
    load(system.file("data", "zebrafishPromoters.RData", package="seqPattern"))
    promoterWidth <- elementMetadata(zebrafishPromoters)$interquantileWidth

    load(system.file("data", "TBPpwm.RData", package="seqPattern"))

    motifOccurrence <- motifScanHits(regionsSeq = zebrafishPromoters,
                                    motifPWM = TBPpwm, minScore = "85%",
                                    seqOrder = order(promoterWidth))
    head(motifOccurrence)

[Package seqPattern version 1.18.0 Index]