Version Compatibility

Reference examples tested with: MACS3 3.0.2+, MACS2 2.2.9+, Genrich 0.6.1+, HMMRATAC 1.2+ (now bundled in MACS3 as macs3 hmmratac), samtools 1.19+, bedtools 2.31+, IDR 2.0.4+.

Before using code patterns, verify installed versions match. If versions differ:

• CLI: <tool> --version then <tool> --help to confirm flags

If code throws unexpected errors, introspect the installed binary (<tool> -h) and adapt the example to match the actual CLI rather than retrying.

ATAC-seq Peak Calling

"Call accessible regions from my ATAC-seq BAM" -> Identify Tn5-hypersensitive open chromatin, treating fragments as point insertion events (not protein-bound regions as in ChIP-seq) and accounting for the lack of input control.

• CLI (canonical, ENCODE 4): macs2 callpeak -t atac.bam -f BAM -g hs -n sample --nomodel --shift -75 --extsize 150 --keep-dup all -B --SPMR -p 0.01 (use -f BAM, not -f BAMPE -- BAMPE reads true fragment ends and ignores --shift/--extsize)
• CLI (HMM-based, single sample): macs3 hmmratac -i atac.bam -n sample --outdir hmm_out
• CLI (joint replicates): Genrich -j -t rep1.bam,rep2.bam -o peaks.narrowPeak -e chrM -E blacklist.bed

The -p 0.01 (loose) plus IDR is the ENCODE pattern: low stringency increases peak overlap between replicates, and IDR rescues the reproducible set. Single-sample workflows usually swap to -q 0.05 instead.