---
title: "Prime Editing Studio (pegRNA)"
method: POST
path: "/prime_editing_design"
tags: ["CRISPR"]
---

# Prime Editing Studio (pegRNA)

`POST /prime_editing_design`

## Request

- Base URL: `https://seqbench.com/api/v1`
- URL: `https://seqbench.com/api/v1/prime_editing_design`
- Auth: none required

Design SpCas9 prime-editing pegRNAs for a substitution, insertion, deletion, or small replacement: for each usable NGG PAM it builds the spacer, a primer-binding-site (PBS) length sweep targeting a ~30 C melting temperature, the reverse-transcriptase template (RTT) that encodes the edit, and the full 3' extension, plus PE3 nicking-sgRNA suggestions 40-90 bp away on the opposite strand. Designs where the edit destroys the pegRNA's own PAM (preventing re-nicking of the edited allele) are ranked first. Coordinates: every pegRNA coordinate (protospacer span, nick position, editStart/editEnd) is 1-based inclusive in the submitted PRE-EDIT target's frame — the protospacer+PAM search runs on the unedited sequence, because Cas9 has to bind the allele you actually have. The one exception is edit-dependent PE3b nicking guides, which exist only once the edit is installed; each nickingGuides entry therefore carries a `coordinateFrame` field of "target" or "editedSequence" naming the frame its own start/end/nickToNickDistance are measured in, and for a length-changing edit the two frames differ downstream of the edit. Off-target activity is not evaluated (no in-browser reference genome).

## Request body

- object
  - `target` string, required: Forward-strand target DNA (raw or FASTA), with flanking sequence around the intended edit.
  - `editStart` integer, required: 1-based inclusive start of the region being changed.
  - `editEnd` integer, required: 1-based inclusive end of the region being changed. For a pure insertion, set editEnd = editStart - 1.
  - `insertedSeq` string: Replacement bases (forward strand). Empty string means a deletion.
  - `rttHomology` integer: Homology length (nt) 3' of the edit that the RTT should include (typically 10-16).
  - `pbsLength` integer: Optional preferred PBS length to highlight; a full 8-17 nt sweep is always returned.
  - `frameStart` integer: Optional 1-based CDS reading-frame start, used only to annotate whether a PAM-blocking mutation would be silent.

## Response `200`

Tool ran successfully.

- SuccessResponse: Standard success envelope returned by every single-tool call.
  - `ok` unknown, required
  - `tool` string, required: The tool slug that ran.
  - `result` object, required: Tool-specific output object. Its shape depends on the tool — call `GET /{tool}` or see the docs for each tool's fields.
  - `gate` GateResult
    - `pass` boolean, required: True if and only if every hard check passed.
    - `checks` GateCheck[], required
      - `id` string, required
      - `label` string, required
      - `severity` 'hard' | 'soft', required
      - `pass` boolean, required
      - `message` string, required
      - `value` number
      - `threshold` string
    - `notChecked` string[], required: Honest list of what this gate does NOT verify.
  - `provenance` Provenance, required
    - `apiVersion` string, required
    - `tool` union, required: Tool slug, or an array of slugs (one per step) for a workflow.
      - string
      - string[]
    - `generatedAt` string, date-time, required: ISO 8601 timestamp of when the result was generated.

## Other responses

- `400`: Invalid argument or the tool could not run.
- `404`: Unknown tool.
- `429`: Rate limited (metered tools only). Body carries code `rate_limited` and retryable `true`; honor the Retry-After header.
- `503`: A metered tool is momentarily at capacity. The identical request should succeed after Retry-After; body carries code `upstream_unavailable`.

---

[API](https://skmtc.dev/seqbench/apis/seqbench-api.md) · [All operations](https://skmtc.dev/seqbench/apis/seqbench-api/llms.txt) · [OpenAPI document](https://skmtc.dev/seqbench/apis/seqbench-api/revisions/132575216865?raw)