hybkit Specification

Version: 0.1.9

The “.hyb” file format is described by Travis, et al. along with the Hyb software package as a “gff-related format that contains sequence identifiers, read sequences, 1-based mapping coordinates, and annotation information for each chimera” (see References).

Each line in a hyb file, referred to here as a hyb “record,” contains information about a genomic sequence read identified to be a chimera by anlaysis sofwtare. Each line contains 15 or 16 columns separated by tab characters (“\t”) and provides information on each of the alignments identified within the sequence read. The columns are described as follows by Travis, et al.:

Column 1, unique sequence identifier.
Column 2, read sequence […].
Column 3, predicted binding energy in kcal/mol.
Columns 4–9, mapping information for first fragment of read: name of matched transcript, coordinates in read, coordinates in transcript, mapping score.
Columns 10–15, mapping information for second fragment of read.
Column 16 (optional, […]), list of annotations in the format: ‘‘feature1=value1; feature2=value2;…”

The hybkit project uses an extended version of this description, including assigning columns reference names, and defining allowed flags.


# Name Description
1 id Hybrid Read Identifier
2 seq Read Nucleotide Sequence
3 energy Predicted Gibbs Free-Energy of Intra-Hybrid Folding
4 seg1_ref Segment 1 Mapping Reference Identity
5 seg1_read_start Segment 1 Mapping Start on Read
6 seg1_read_end Segment 1 Mapping End on Read
7 seg1_ref_start Segment 1 Mapping Start on Reference
8 seg1_ref_end Segment 1 Mapping End on Reference
9 seg1_score Segment 1 Mapping Score
10 seg2_ref Segment 2 Mapping Reference Identity
11 seg2_read_start Segment 2 Mapping Start on Read
12 seg2_read_end Segment 2 Mapping End on Read
13 seg2_ref_start Segment 2 Mapping Start on Reference
14 seg2_ref_end Segment 2 Mapping End on Reference
15 seg2_score Segment 2 Mapping Score
16 flags Hybrid Read Analysis Details


Hyb Flags:

The following four flags are used by the Hyb software package (see References). The definitions provided describe how these flags are used in the hybkit package.

count_total - Integer: Total represented hybrid records, if combined.

count_last_clustering - Integer: Total represented hybrid records at last clustering.

two_way_merged - {“0” or “1”} Boolean representation of whether entries with mirrored 5’ and 3’ hybrids were merged if the record is a combined record.

seq_IDs_in_cluster - String: Comma-separated list of all reord IDs of hybrids merged into this hybrid entry.

The following flags are defined by the hybkit package:

read_count - Integer: Number of sequence reads represented by this record. If the record is combined, this represents the total read count for all merged entries.

orient - String: Orientation of strand. Options: “F” (Forward), “IF” (Inferred Forward), “R” (Reverse), “IR” (Inferred Reverse), “U” (Unknown), or “IC” (Inferred Conflicting).

seg1_type - String: Assigned segment type of segment 1, ex: “miRNA” or “mRNA”.

seg2_type - String: Assigned segment type of segment 2, ex: “miRNA” or “mRNA”.

seg1_det - String: Arbitrary detail about segment 1.

seg2_det - String: Arbitrary detail about segment 2.

miRNA_seg - String: Indicates which (if any) segment mapping is a miRNA options are “N” (none), “3p” (seg1), “5p” (seg2), “B” (both), or “U” (unknown).

target_reg - String: Assigned region of the miRNA target. options are “5pUTR”, “coding”, “3pUTR”, “N” (none), or “U” (unknown).

ext - Integer: “0” or “1”, Boolean representation of whether record sequences were bioinformatically extended as is performed by the Hyb software package.

source - String: Label for sequence source id (eg. source file), when combining records from different sources.

Other Details

Item Role
\t Column Delimiter
. Missing Data Placeholder (equivalent to None)
.hyb File Suffix
.hyb.gz gzipped File Suffix


An example .hyb format line (courtesy of Gay et al. [References]):

2407_718    ATCACATTGCCAGGGATTTCCAATCCCCAACAATGTGAAAACGGCTGTC       .       MIMAT0000078_MirBase_miR-23a_microRNA   1       21      1       21      0.0027  ENSG00000188229_ENST00000340384_TUBB2C_mRNA     23      49      1181    1207    1.2e-06