packSearch {packFinder} | R Documentation

## packFinder Algorithm Pipeline

### Description

General use pipeline function for the Pack-TYPE transposon finding algorithm.

### Usage

    packSearch(
      tirSeq,
      Genome,
      mismatch = 0,
      elementLength,
      tsdLength,
      tsdMismatch = 0
    )

### Arguments

`tirSeq` | A `DNAString` object containing the TIR sequence to be searched for.
`Genome` | A `DNAStringSet` object to be searched.
`mismatch` | The maximum edit distance to be considered for TIR matches (indels + substitions). See `matchPattern` for details.
`elementLength` | The maximum element length to be considered, as a vector of two integers. E.g. `c(300, 3500)`
`tsdLength` | Integer referring to the length of the flanking TSD region.
`tsdMismatch` | An integer referring to the allowable mismatch (substitutions or indels) between a transposon's TSD sequences. `matchPattern` from Biostrings is used for pattern matching.

### Details

Finds potential pack-TYPE elements based on:

- Similarity of TIR sequence to `tirSeq`

- Proximity of potential TIR sequences

- Directionality of TIR sequences

- Similarity of TSD sequences

The algorithm finds potential forward and reverse TIR sequences using `identifyTirMatches` and their associated TSD sequence via `getTsds`. The main filtering stage, `identifyPotentialPackElements`, filters matches to obtain a dataframe of potential PACK elements. Note that this pipeline does not consider the possibility of discovered elements being autonomous elements, so it is recommended to cluster and/or BLAST elements for further analysis. Furthermore, only exact TSD matches are considered, so supplying long sequences for TSD elements may lead to false-negative results.

### Value

A dataframe, containing elements identified by thealgorithm. These may be autonomous or pack-TYPE elements. Will contain the following features:

- start - the predicted element's start base sequence position.

- end - the predicted element's end base sequence position.

- seqnames - character string referring to the sequence name in `Genome` to which `start` and `end` refer to.

- width - the width of the predicted element.

- strand - the strand direction of the transposable element. This will be set to "*" as the `packSearch` function does not consider transposons to have a direction - only TIR sequences. Passing the `packMatches` dataframe to `packClust` will assign a direction to each predicted Pack-TYPE element.

This dataframe is in the format produced by coercing a `link[GenomicRanges:GRanges-class]{GRanges}` object to a dataframe: `data.frame(GRanges)`. Downstream functions, such as `packClust`, use this dataframe to manipulate predicted transposable elements.

### Note

This algorithm does not consider:

- Autonomous elements - autonomous elements will be predicted by this algorithm as there is no BLAST step. It is recommended that, after clustering elements using `packClust`, the user analyses each group to determine which predicted elements are autonomous and which are likely Pack-TYPE elements. Alternatively, databases such as Repbase (https://www.girinst.org/repbase/) supply annotations for autonomous transposable elements that can be used to filter autonomous matches.

- TSD Mismatches - if two TIRs do not have exact matches for their terminal site duplications they will be ignored. Supplying longer TSD sequences will likely lead to a lower false-positive rate, however may also cause a greater rate of false-negative results.

Pattern matching is done via `matchPattern`.

### Author(s)

Jack Gisby

### See Also

`identifyTirMatches`, `getTsds`, `identifyPotentialPackElements`, `packClust`, `packMatches`, `DNAStringSet`, `DNAString`, `matchPattern`

### Examples

    data(arabidopsisThalianaRefseq)

    packMatches <- packSearch(
        Biostrings::DNAString("CACTACAA"),
        arabidopsisThalianaRefseq,
        elementLength = c(300, 3500),
        tsdLength = 3
    )

[Package packFinder version 1.2.0 Index]