FB2026_02 , released June 18, 2026
Physical Interaction report
Open Close
General Information
Interaction Type
Interacting Genes
FlyBase ID
FBig0000099499
Interaction Network
Interactions Browser links
Su(var)205 network
Su(var)2-HP2 network
Reported Interactions
FBrf0152321-1.Y2H
Description
physical association
Assay
Collection
Source/Stage
Cell line used
Participants
Corresponds to
Reported as
Role
Note

HP1

bait

fused to LexA DNA-binding domain

HP2

prey

fused to B42 activation domain

Experimental entities
Corresponds to
Identifier
Reported
Role
Note
Subregions with role in interaction
Corresponds to
Description
Role
Coordinates
Note
C-terminal region
sufficient binding region
aa 95-206
Isoform-specific participants
Corresponds to
Description
Role
Note
Comments concerning this interaction

Source was yeast cell line; bait produced as transgenic fusion protein; prey produced as transgenic fusion protein (prey from embryo cDNA expression library).

Two-hybrid system: yeast LexA-BD/B42-AD

FBrf0152321-3.coIP.A
Description
physical association
Collection
Source/Stage
Cell line used
Participants
Corresponds to
Reported as
Role
Note

HP1

bait

HP2

prey

[35]S label

Experimental entities
Corresponds to
Identifier
Reported
Role
Note
Subregions with role in interaction
Corresponds to
Description
Role
Coordinates
Note
Isoform-specific participants
Corresponds to
Description
Role
Note
Comments concerning this interaction

Interaction in vitro; bait derived from wild-type embryonic extract; prey synthesized by in vitro translation.

Two-hybrid system: yeast LexA-BD/B42-AD

FBrf0189850-1.PD.A
Description
physical association
Collection
Source/Stage
Cell line used
Participants
Corresponds to
Reported as
Role
Note

HP1

bait

[35]S label

HP2

prey

[35]S label

Experimental entities
Corresponds to
Identifier
Reported
Role
Note
Subregions with role in interaction
Corresponds to
Description
Role
Coordinates
Note
interaction domain
sufficient binding region
aa 2433-2479

coordinates relative to (Block H, Block G and the 19aa linker between the two) Su(var)2-HP2-PA

block H domain
mutation disrupting interaction
aa 2468, 2472, 2478

V2468E,R2472E,W2478E, coordinates relative to Su(var)2-HP2-PA

Isoform-specific participants
Corresponds to
Description
Role
Note
Comments concerning this interaction

Mutation of the H block abrogates binding, however the H block is not sufficient for binding. G and H blocks plus the 19aa linker between the 2 are sufficient for binding.

Interaction in vitro; bait produced and labeled by in vitro translation; prey produced and labeled by in vitro translation.

FBrf0194422-3.CH.WB
Description
physical association
Collection
Source/Stage
Cell line used
Participants
Corresponds to
Reported as
Role
Note

HP2

neutral component

HP2

neutral component

HP2

neutral component

HP1

neutral component

HP1

neutral component

HP1

neutral component
Experimental entities
Corresponds to
Identifier
Reported
Role
Note
Subregions with role in interaction
Corresponds to
Description
Role
Coordinates
Note
Isoform-specific participants
Corresponds to
Description
Role
Note
Comments concerning this interaction

Source was embryos of wild-type fly line; proteins produced from endogenous genes.

FBrf0208478-1.coIP.WB
Description
physical association
Collection
Source/Stage
Cell line used
Participants
Corresponds to
Reported as
Role
Note

HP1

bait

HP2

prey
Experimental entities
Corresponds to
Identifier
Reported
Role
Note
Subregions with role in interaction
Corresponds to
Description
Role
Coordinates
Note
Isoform-specific participants
Corresponds to
Description
Role
Note
Comments concerning this interaction

Source was adults of wild-type fly line; bait produced from endogenous gene; prey produced from endogenous gene.

Positive control.

FBrf0213514-1.NMR
Description
physical association
Collection
Source/Stage
Cell line used
Participants
Corresponds to
Reported as
Role
Note

Su(var)205

unspecified role

His Tag

Su(var)205

unspecified role

His Tag

Su(var)205

unspecified role

His Tag

Su(var)2-HP2

unspecified role

His Tag

Su(var)2-HP2

unspecified role

His Tag

Su(var)2-HP2

unspecified role

His Tag

Experimental entities
Corresponds to
Identifier
Reported
Role
Note
Subregions with role in interaction
Corresponds to
Description
Role
Coordinates
Note
chromo shadow domain (CSD)
sufficient binding region
aa 131-206
interaction domain
sufficient binding region
aa 2414-2512

coordinates relative to Su(var)2-HP2-PA

Isoform-specific participants
Corresponds to
Description
Role
Note
Comments concerning this interaction

Interaction in vitro; proteins produced as recombinant fusion proteins in bacterial system.

NMR suggests Trp 2478 of Su(var)2-HP2 involved in binding Su(var)205 CSD.

FBrf0213514-11.CS.MW
Description
physical association
Collection
Source/Stage
Cell line used
Participants
Corresponds to
Reported as
Role
Note

Su(var)205

neutral component

Su(var)205

neutral component

Su(var)205

neutral component

Su(var)2-HP2

neutral component

Su(var)2-HP2

neutral component

Su(var)2-HP2

neutral component
Experimental entities
Corresponds to
Identifier
Reported
Role
Note
Subregions with role in interaction
Corresponds to
Description
Role
Coordinates
Note
chromo shadow domain (CSD)
sufficient binding region
aa 131-206
chromo shadow domain (CSD) residue 195
mutation decreasing interaction
aa 195

E195Q

interaction domain
sufficient binding region
aa 2459-2480

coordinates relative to Su(var)2-HP2-PA

Isoform-specific participants
Corresponds to
Description
Role
Note
Comments concerning this interaction

Interaction in vitro; protein produced as a recombinant fusion protein in bacterial system.

FBrf0213514-2.coIP.A
Description
physical association
Collection
Source/Stage
Cell line used
Participants
Corresponds to
Reported as
Role
Note

Su(var)205

bait

[35]S label

Su(var)2-HP2

prey

[35]S label

Experimental entities
Corresponds to
Identifier
Reported
Role
Note
Subregions with role in interaction
Corresponds to
Description
Role
Coordinates
Note
interaction domain residue 200
mutation disrupting interaction
aa 200

W200A

interaction domain residue 191
mutation disrupting interaction
aa 191

I191E

interaction domain
sufficient binding region
aa 2414-2512

coordinates relative to Su(var)2-HP2-PA

interaction domain residue 2468
mutation disrupting interaction
aa 2468

V2468E, coordinates relative to Su(var)2-HP2-PA

Isoform-specific participants
Corresponds to
Description
Role
Note
Comments concerning this interaction

Interaction in vitro; bait produced and labeled by in vitro translation; prey produced and labeled by in vitro translation.

FBrf0213514-6.CH.MW
Description
physical association
Collection
Source/Stage
Cell line used
Participants
Corresponds to
Reported as
Role
Note

Su(var)205

neutral component

His Tag

Su(var)205

neutral component

His Tag

Su(var)205

neutral component

His Tag

Su(var)2-HP2

neutral component

His Tag

Su(var)2-HP2

neutral component

His Tag

Su(var)2-HP2

neutral component

His Tag

Experimental entities
Corresponds to
Identifier
Reported
Role
Note
Subregions with role in interaction
Corresponds to
Description
Role
Coordinates
Note
chromo shadow domain (CSD)
sufficient binding region
aa 131-203
interaction domain
sufficient binding region
aa 2414-2512

coordinates relative to Su(var)2-HP2-PA

Isoform-specific participants
Corresponds to
Description
Role
Note
Comments concerning this interaction

Interaction in vitro; proteins produced as recombinant fusion proteins in bacterial system.

Stoichiometry is 2 Su(var)205 : 1 Su(var)2-HP2.

FBrf0213514-7.FPS
Description
physical association
Collection
Source/Stage
Cell line used
Participants
Corresponds to
Reported as
Role
Note

Su(var)205

bait

His Tag

Su(var)2-HP2

prey

fluorescein label

Experimental entities
Corresponds to
Identifier
Reported
Role
Note
Subregions with role in interaction
Corresponds to
Description
Role
Coordinates
Note
chromo shadow domain (CSD)
sufficient binding region
aa 131-206
interaction domain residue 191
mutation decreasing interaction
aa 191

I191E

interaction domain residues 199, 202
mutation increasing interaction
aa 199, 202

S199E, S202E

interaction domain residues 204-206
mutation increasing interaction
aa 204-206
interaction domain residue 200
mutation decreasing interaction
aa 200

W200A

interaction domain
sufficient binding region
aa 2459-2480

coordinates relative to Su(var)2-HP2-PA

Isoform-specific participants
Corresponds to
Description
Role
Note
Comments concerning this interaction

Interaction in vitro; bait produced as a recombinant fusion protein in bacterial system; prey peptide chemically synthesized and labeled in vitro.

FBrf0222287-5.FPS
Description
physical association
Collection
Source/Stage
Cell line used
Participants
Corresponds to
Reported as
Role
Note

HP1a

bait

His tag

HP2

prey

fluorescein label

Experimental entities
Corresponds to
Identifier
Reported
Role
Note
Subregions with role in interaction
Corresponds to
Description
Role
Coordinates
Note
chromo shadow domain and C-terminal extension
sufficient binding region
aa 141-206
C-terminal extension
mutation decreasing interaction
aa 205aa 206

E205Q, 4-fold decrease

D206N, 4-fold decrease

chromo shadow domain
mutation decreasing interaction
aa 147aa 153aa 177aa 181aa 165

L147K, 3-fold decrease

L153K, 30-fold decrease

V177K, over 20-fold decrease

V181K

L165K, 20-fold decrease

PXVXL motif
sufficient binding region
QNISPRKLSVKINRRPYNKWLR

PXVXL motif = LSVKI

Isoform-specific participants
Corresponds to
Description
Role
Note
Comments concerning this interaction

Interaction in vitro; bait produced as a recombinant fusion protein in bacterial system; prey peptide chemically synthesized and labeled in vitro.

Su(var)205 binds various proteins containing the PXVXL with different affinities. Binding is strongest to Su(var)2-HP2 (Kd = 0.27 uM). Su(var)205 also binds woc (Kd = 2.47 uM) and piwi (12.8 uM) much more weakly.

The Su(var)205 R188Q mutation, which affects Su(var)205 homodimerization, has little effect on the binding constant of this interaction.

Residue Leu 165 of Su(var)205 is critical for selective high-affinity binding of Su(var)205 to Su(var)2-HP2 over piwi. Mutation L165K drastically reduces the Su(var)205-Su(var)2-HP2 interaction, with little effect on binding to piwi.

FBrf0225528-3.coIP.MS
Description
physical association
Collection
Source/Stage
Cell line used
Participants
Corresponds to
Reported as
Role
Note

HP1a

bait

BioTAP tag

Su(var)2-HP2

prey

68 unique peptides identified

Experimental entities
Corresponds to
Identifier
Reported
Role
Note
Subregions with role in interaction
Corresponds to
Description
Role
Coordinates
Note
Isoform-specific participants
Corresponds to
Description
Role
Note
Comments concerning this interaction

Source was cross-linked nuclear extract of S2 cell line; bait produced from transfected construct; prey produced from endogenous gene.

Crude nuclear extracts were cross-linked using formaldehyde, sonicated, and subjected to ProteinA affinity purification with rabbit IgG agarose beads eluted under denaturing conditions, and subsequently using streptavidin agarose beads for Bio affinity purification. Purified peptides were eluted by on-bead trypsin digestion and mass spectrometric analysis.

Enrichment of prey protein was compared to input, mock and unrelated BioTAP affinity purifications using a statistical method (Bamse) developed by the authors to control for multiple sources of bias.

FBrf0225528-49.coIP.MS
Description
physical association
Collection
Cell line used
Participants
Corresponds to
Reported as
Role
Note

HP1a

bait

BioTAP tag

HP2

prey

72 unique peptides identified

Experimental entities
Corresponds to
Identifier
Reported
Role
Note
Subregions with role in interaction
Corresponds to
Description
Role
Coordinates
Note
Isoform-specific participants
Corresponds to
Description
Role
Note
Comments concerning this interaction

Source was cross-linked nuclear embryonic extract of transgenic fly line; bait produced from tagged transgenic construct; prey produced from endogenous gene.

Crude nuclear extracts were cross-linked using formaldehyde, sonicated, and subjected to ProteinA affinity purification with rabbit IgG agarose beads eluted under denaturing conditions, and subsequently using streptavidin agarose beads for Bio affinity purification. Purified peptides were eluted by on-bead trypsin digestion and mass spectrometric analysis.

Enrichment of prey protein was compared to input, mock and unrelated BioTAP affinity purifications using a statistical method (Bamse) developed by the authors to control for multiple sources of bias.

FBrf0225528-55.coIP.MS
Description
physical association
Collection
Cell line used
Participants
Corresponds to
Reported as
Role
Note

HP1a

bait

BioTAP tag

HP2

prey

59 unique peptides identified

Experimental entities
Corresponds to
Identifier
Reported
Role
Note
Subregions with role in interaction
Corresponds to
Description
Role
Coordinates
Note
Isoform-specific participants
Corresponds to
Description
Role
Note
Comments concerning this interaction

Source was cross-linked nuclear larval extract of transgenic fly line; bait produced from tagged transgenic construct; prey produced from endogenous gene.

Crude nuclear extracts were cross-linked using formaldehyde, sonicated, and subjected to ProteinA affinity purification with rabbit IgG agarose beads eluted under denaturing conditions, and subsequently using streptavidin agarose beads for Bio affinity purification. Purified peptides were eluted by on-bead trypsin digestion and mass spectrometric analysis.

Enrichment of prey protein was compared to input, mock and unrelated BioTAP affinity purifications using a statistical method (Bamse) developed by the authors to control for multiple sources of bias.

FBrf0225528-61.coIP.MS
Description
physical association
Collection
Source/Stage
Cell line used
Participants
Corresponds to
Reported as
Role
Note

HP1a

bait

BioTAP tag

HP2

prey

46 unique peptides identified

Experimental entities
Corresponds to
Identifier
Reported
Role
Note
Subregions with role in interaction
Corresponds to
Description
Role
Coordinates
Note
Isoform-specific participants
Corresponds to
Description
Role
Note
Comments concerning this interaction

Source was cross-linked nuclear extract of transgenic fly line; bait produced from tagged transgenic construct; prey produced from endogenous gene.

Crude nuclear extracts were cross-linked using formaldehyde, sonicated, and subjected to ProteinA affinity purification with rabbit IgG agarose beads eluted under denaturing conditions, and subsequently using streptavidin agarose beads for Bio affinity purification. Purified peptides were eluted by on-bead trypsin digestion and mass spectrometric analysis.

Enrichment of prey protein was compared to input, mock and unrelated BioTAP affinity purifications using a statistical method (Bamse) developed by the authors to control for multiple sources of bias.

External Crossreferences and Linkouts ( 1 )
Linkouts
MIST - An integrated Molecular Interaction Database
References (7)