anchorna 2.0.0
Find anchors in RNA/DNA sequences
Keywords: bioinformatics, RNA, DNA, sequence, anchors

### AnchoRNA

Find anchors in RNA/DNA sequences.

AnchoRNA is designed to find anchors, i.e. conserved regions, in coding sequences in a set of similar sequences. Anchors are stored as GFF files.
Anchors can be viewed in JalView. You can cut out sequences relative to anchors for import into external tools.

AnchoRNA supports curation and iterative refinement of anchors. It can also be used to find anchors in non-coding sequences or amino acid sequences.

### Installation

Use pip to install anchorna. It is best installed in a dedicated (conda) environment.

```
pip install anchorna
```

To install the latest development version, use:

```
pip install https://github.com/rnajena/anchorna/archive/refs/heads/master.zip
```

To install the package in editable mode, clone the repository and install with `pip -e repo_path`.

### Usage & Tutorial

The motivation, algorithm and performance of AnchoRNA are described in the following preprint:

Tom Eulenfeld, Sandra Triebel, Manja Marz (2025),
AnchoRNA: Full virus genome alignments through conserved anchor regions,
doi:[10.1101/2025.01.30.635689](https://doi.org/10.1101/2025.01.30.635689)
[[pdf](https://www.biorxiv.org/content/10.1101/2025.01.30.635689.full.pdf)]

A command line tool is provided, see `anchorna -h` and the help of subcommands. An example configuration file can be created with `anchorna create`.
See the example configuration file for a description of AnchoRNA's options. Consult the [API documentation](https://anchorna.readthedocs.io) for details.

Please first get an overview of the available commands with

```
anchorna -h
```

Help is available for each command, e.g. try `anchorna go -h`.

Start the tutorial with

```
anchorna create --tutorial
```

We provide here some CLI calls. Please run each of them separately and carefully try to understand what they do.

```
# Identify anchors, use 8 cores
anchorna go --njobs 8 anchors.gff

# Print anchors
anchorna print anchors.gff
anchorna print -v anchors.gff
anchorna print --mode nt anchors.gff

# View anchors in Jalview (amino acid sequences) and
# align with the second anchor
anchorna view anchors.gff --align A1
# For reference, the following commands are called under the hood
# by anchorna view
#anchorna export anchors.gff --fmt jalview -o jalview_fts.txt
#sugar translate --cds pesti_example.gff -o pestiaa.fasta
#jalview pestiaa.fasta --features jalview_fts.txt

# View anchors in Jalview (nucleotide sequences)
anchorna view --mode nt anchors.gff

# We are not satisfied with the anchor 8, remove it and check the resulting anchors in
# Jalview, afterwards save to new anchor file
anchorna combine "anchors.gff||a8" | anchorna view -
anchorna combine "anchors.gff||a8" -o anchors2.gff
# Note that anchors are renumbered, the anchor number is not a property of each anchor,
# it is just used as a simple reference later on
anchorna print anchors2.gff

# Cutout subsequences starting before start codon and ending 10 nucleotides
# after 3rd anchor (remember 0-based indexing) for usage in external tool
anchorna cutout anchors2.gff "ATG" "A2+10" -o pestiA3.fasta

# <, > can be used to specify left and right end of anchor, ^ to reference the middle position,
# by default the anchor is included in the cutout, therefore the above call is the same as
#anchorna cutout anchors2.gff "ATG<" "A2>+10" -o pestiA3.fasta



### Advanced
# Load anchors into IPython session
anchorna load anchors2.gff

# Run anchorna on subsequences and combine results into a single anchor file
# We are not satisfied with the long region (~ 2000 nt) without any anchors,
# find two anchors immediately before and after this "empty" region with
anchorna view anchors2.gff

# The following command is a bit long, but it does the job well.
# It cuts out sequences between the two anchors
# (please replace the ?? characters with the anchors around the "empty region")
# and writes the sequences to stdout, which is piped into the next command.
# --fmt sjson makes this work, because we need to preserve some metadata,
# which is not guaranteed by fasta, the default output format.
# anchorna go --fname - tells anchorna to run the algorithm with the subsequences from stdin.
# Also, some options are relaxed to find more anchors in this region.
anchorna cutout anchors2.gff "A??>" "A??<" --fmt sjson | anchorna go --fname - --thr-quota-add-anchor 0.9 anchors_sub.gff

# We found more anchors and investigate these
anchorna print anchors_sub.gff
anchorna view anchors_sub.gff
# Finally we merge the two anchor files
anchorna combine anchors2.gff anchors_sub.gff -o anchors_final.gff
anchorna print anchors_final.gff
anchorna view anchors_final.gff
```

### Run tests

Clone or download this repository cd into tests folder and call `pytest`.

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[<img src="https://raw.github.com/rnajena/sugar/logo/sugar_logo.png" alt="sugar_logo" width="200">](https://github.com/rnajena/sugar)