Volume
0
295. number
I .2,3, l-2
FEBS
10536
Dcccmher
1991
1991 Fcdcration or European Biochemical Socictics 00145793/91/S3.50
Hypothesis
(HX),, repeats: a pH-controlled protein-protein interaction eukaryotic transcription factors? Kalf Janknecht’, ’ Itrsrinrt Ji’ir ~Molcktrl~trbiologie, 2Ewoperttt
Mokculur
Biology
Chris
Sander’
motif of
and Olaf Pangs’
Medizittisclte Hocl~scl~trlc Hnrrrtove~. ~ottstNttt~-Glrr.selto,~l-Strusse 8. D-3000 Hmttover. Germuty, AI~~~~crlt~~,~t~~~Nsse I I D-6900 Hcidelbcrg, Gcrtttutry and 3Leltr.wdtl fiir Biodtettric~. RdtrLaborutoty. Uttiwrsitdt Bocltwtt. L/‘rtirer:vitiitssrrus.~e 1%. D-4630 Bocltwtt. Gertttutty
Received 3 I October 1991 A characteristic scqucncc repeat of type His-X. rcpeatcd scvcral times in a row. is prcscnl in several eukaryotic transcription factors. c.g. HPHAHPHP in pui~d prolcin. Dctai!ed molecular modelling and database searches lead 10 the suggestion that (HX), rcpcats can mediate interaction between transcription factors in a pH-controlled fashion. Gcnc rcgulalion; Transcription ractor; Dimcrizalion; Zn-binding: Sequ-ncc analysis
(HX),, repeats were first observed in the His-Pro-rich PRD domain of the Drosophih paired protein [I] and aroused our interest as part of the efs-oncoprotein related Drosophilct 74E gene products [2]. A subsequent systematic search for significant (HX),, repeats in the databases of known protein sequences yielded mostly further Drosophilu transcription factors (Fig. 1): Bicoid [3], Deformed [4], Odd-Skipped [S], Daughterless [6], Cfla [7], and E75A [8]. Other proteins found with this pattern were a chicken transcription factor (Chox-1.4 [9]), the rabbit T-cell receptor /?-chain precursor (TCR [lo]), the tobacco acetolactate synthase precursor (ALSSuRA [l I]), and the Herpes latency-related proteins 1 and 2 (Lrpl and Lrp2 [12]). (HX),, repeats in proteins with polyhistidine stretches or with unusually high histidine content were not regarded as significant. Analysis of the (HX),, repeats shows that X is preferentially P (Pro)? S (Ser), H (His), A (Ala) or T (Thr) and that the multiplicity of the repeat ranges from 1t=2 to tt=I I (Fig. I\ L F--t IUV\ I). x1 ~voie iitlii -_.._1.._..,___ ua,u&11rr11~53 1183 a nearly pcr~c~ ,.I,.,,a repeat, with Leu in place of His at positions 233, 235, 239 and 245. The predominant occurrence of (HX),, repeats in Drosophilu transcription factors hints at a common functional interpretation of this sequence motif. WC suggest the hypothesis that (HX),, repeats mediate protein-protein interactions, which are known to be a necessary prerequisite for the function of transcription factors, in a PI-l-dependent fashion. Structurally, (I-IX),, repeats in Corrc.~potrt/~ttrc adhm: C. Sander, Europcdn Molecular Biology Laboratory, Mcycrholj;trasse I. D-G900 Hcidclbcrg. Germany. Fax: (49) (6221) 38 7306.
an extended conformation can present linear arrays of His side chains, which can associate in pairs by coordinating metal ions like Zn” or Cu” (Fig. 2). This structure could be termed a ‘histidine-metal zipper’. Consistent with this structural model is the observation in known three-dimensional structures that Pro often occurs adjacent to His in metal binding sites of enzymes 1131.
Interacting (HX),, repeats could guide the formation of dimers or of networks of transcription factors. An example may be the 74E gene products and E75A, which have been shown to bind to early and late puffs on Drosophih polytene chromosomes, after induction of third larval instar salivary glands with 20-hydroxyecdysone (for a review see [14]). It is tempting to speculate that this coordinated binding involves interaction via the (HX),, repeats. An intriguing property of protein-protein interactions mediated by (HX),, would be sensitivity to pH. As the p.& of a hicrid;nP side chain is in the range of phy...-_.- _.___.__ siological pH values, a small shift in intracellular p!-l could have a dramatic effect on the binding capacity of (HX),, repeats. By this mechanism extracellular inductors like growth factors, which can increase lhc intracellular pH by 0.1-0.3 units [IS], might influcncc the association state of an entire network of transcription factors. At the present stage of limited experimental evidence we cannot exclude the possibility of other functional roles of (HX),, repeats: for example, direct binding to DNA or RNA through H-bonds from His side chains to phosphate groups; or, interaction with the acidic do-
December
FEBSLETTERS
Volume295, number1,2,3
199
74E:
658
QwqHPHSql
ngpHPHSH?H
SHPHSHPHAg
qtXHStiaaa
697
Paired:
544
gHAHSHHgHP
HApHPHAHPH
PqyzlgaHPHY
pppsssaHFm
583
Bicoid:
10
fyHHplpHTH
THPHPHSHPH
PHSHPHPHHq
49
Deformed:
73
mtgHPHSmHP
admvsdymaH
HHNpHSHSHS
HPqlqlppqf HTHSlpHHHS
112
113
nsaisgHHqa
saggysrnya
natppsHPHS
HPHAHPHQsl
152
Odd-Skipped:
237
qqqHPHHHHh
HGHPhHPHPH
PHHvrpypag
176
Daughterless:
219
naaiyqqqqq HHslnHTpHA
HSHTlplpHA
1pHGiiTlpHP H;isqqnspav
258
Cfla:
298
HHggyHPHHd
mHGspmgtX
HSHSppmlsp
qnmqssavaa
237
";75A:
156
HHHPqqeHQp
hHPHPHVmyp
HGyqqanlHH
195
Chox-1.4:
26
HSgsagssas
qwqgqHHlq yHPhHPHPHA
EiLHAaHPgpa
65
TCR:
48
sHTHRHSyl1
HPHTHVct3T
PPPPPPPPPP HTctHTHIHA
stHVciHTHT
87
ALS-SuRA:
33
fpfpIiHpHKt
tpppIHLtHT
HIHIHSqrrr
ftisnvistn
72
Lrpl:
31
HPHSHApplp
rtptps!iPHS
rasplprapt
ptHPHSHApp
70
Lrp2:
13
HPHSHApplp
rtptpaHPHS
HApplprtpt
ptHPHSHApp
52
Fig.
I. Partial sequences of proteins, primarily
mmscription factors, containing significant (HX),: repeats. The sequences are not slrictly aligncc HX sequences are in capital lelrcrs. Prolcin codes are explained in Uie text.
mains of other transcription factors, which are thou@ to pass stimulatory signals to the transcription machil: ery by interacting with TFIID orTFIIB [16]. We hope that our hypothesis of pH-dependent prc tein-protein interaction between transcription factor mediated by (HX),, repeats will stimulate specific exper. ments. REFERENCES Frigerio. 111
Fig. 2. Approximale molecular model of Iwo PHPHP units imcracting via a bound metal ion. Only IWO HX units arranged ir. antiparallcl are shown here. Longer. zipper-like rcpcaring structures can be generated without violation of stcrcochemislry by simple lalcral displaccmcm in thedirection ofthepolypeptidc backbone. The association of two (HX),, repeats is likely to bc pH.dcpendcnt in the relatively narrow range of inlracellular pH values available to physiological control.
2
G., Burri. M., Bopp, D., Baumgartner. S. and Nell. h (1986) Cell 47, 735-746. v1Janknecht, R., Taube, W., Liidecke, H.-J. and Pangs, 0. (I981 Nucleic Acids Rcs. 17, 4455-4464. 131 Ucrleth, T., Burri. M.. Thoma, G., Bopp, D., Richslcin, S., Prig rio, G., Nell, M. and NUs!ein-Volhard, C. (1988) EMBO J. 1749-1756. R&ski. M., >lcGinnis, N., Chadwick, R. and *McGinnis. V (1987) EMBO J. 6, 767-777. Coulter, D.E.. Swaykus, E.A., Bcran-Kochn, MA., Goldb:: ..__.. D., Wieschaus, E. and Schedi. P. (IWU) EMBO J, 8, 3795-330 Cronmiller, C., Schedl, P. and Clint, T.W. (1988) Genes Dev. lG66-1676. Johnson, W.A. andHirsh, J. (1990) Nature 343,467-470. Segraves, W.A. and Hogncss, D.S. (1990)Gcnes Dcv. 4,204-21 Sasaki, H.. Yokoyama, E. and Kuroiwa. A. (1990)Nucleic Acil Res. 18, 1739-1747. [!O] Angiolillo, A.L., Lamoyi, E., Bernstein, K.E. and Mage, R.( 119851 Proc. Nail. Acad. Sci. USA 82.4498-450!. [I I] iec, K.Y., Townsend, J., Tcpperman,.J., Black, U.. Chui, C.F Mazur, B., Dunsmuir. P. nnd Bedbrook, J. (1985) EMBO J. 1241-1248. [I21 Wcchsler, S-L., Ncsburn, A.B., Zwaagstra, J. nnd Ghiasi, I (1989) Virology 168, 168-172. [l3] Chakrabani, P, (1990) Prot. Engineering 4. 57-63, [I41 Thummcl, C.S. (1990) BioEssays 12, 561-568. [IS] Moolenaar, W.H. (1986) Ann. Rev. Physiol. 48, 363-376. [lb] Sharp, P.A. (1991) Nalurc 351, 16-18.
0
295. number
I .2,3, l-2
FEBS
10536
Dcccmher
1991
1991 Fcdcration or European Biochemical Socictics 00145793/91/S3.50
Hypothesis
(HX),, repeats: a pH-controlled protein-protein interaction eukaryotic transcription factors? Kalf Janknecht’, ’ Itrsrinrt Ji’ir ~Molcktrl~trbiologie, 2Ewoperttt
Mokculur
Biology
Chris
Sander’
motif of
and Olaf Pangs’
Medizittisclte Hocl~scl~trlc Hnrrrtove~. ~ottstNttt~-Glrr.selto,~l-Strusse 8. D-3000 Hmttover. Germuty, AI~~~~crlt~~,~t~~~Nsse I I D-6900 Hcidelbcrg, Gcrtttutry and 3Leltr.wdtl fiir Biodtettric~. RdtrLaborutoty. Uttiwrsitdt Bocltwtt. L/‘rtirer:vitiitssrrus.~e 1%. D-4630 Bocltwtt. Gertttutty
Received 3 I October 1991 A characteristic scqucncc repeat of type His-X. rcpeatcd scvcral times in a row. is prcscnl in several eukaryotic transcription factors. c.g. HPHAHPHP in pui~d prolcin. Dctai!ed molecular modelling and database searches lead 10 the suggestion that (HX), rcpcats can mediate interaction between transcription factors in a pH-controlled fashion. Gcnc rcgulalion; Transcription ractor; Dimcrizalion; Zn-binding: Sequ-ncc analysis
(HX),, repeats were first observed in the His-Pro-rich PRD domain of the Drosophih paired protein [I] and aroused our interest as part of the efs-oncoprotein related Drosophilct 74E gene products [2]. A subsequent systematic search for significant (HX),, repeats in the databases of known protein sequences yielded mostly further Drosophilu transcription factors (Fig. 1): Bicoid [3], Deformed [4], Odd-Skipped [S], Daughterless [6], Cfla [7], and E75A [8]. Other proteins found with this pattern were a chicken transcription factor (Chox-1.4 [9]), the rabbit T-cell receptor /?-chain precursor (TCR [lo]), the tobacco acetolactate synthase precursor (ALSSuRA [l I]), and the Herpes latency-related proteins 1 and 2 (Lrpl and Lrp2 [12]). (HX),, repeats in proteins with polyhistidine stretches or with unusually high histidine content were not regarded as significant. Analysis of the (HX),, repeats shows that X is preferentially P (Pro)? S (Ser), H (His), A (Ala) or T (Thr) and that the multiplicity of the repeat ranges from 1t=2 to tt=I I (Fig. I\ L F--t IUV\ I). x1 ~voie iitlii -_.._1.._..,___ ua,u&11rr11~53 1183 a nearly pcr~c~ ,.I,.,,a repeat, with Leu in place of His at positions 233, 235, 239 and 245. The predominant occurrence of (HX),, repeats in Drosophilu transcription factors hints at a common functional interpretation of this sequence motif. WC suggest the hypothesis that (HX),, repeats mediate protein-protein interactions, which are known to be a necessary prerequisite for the function of transcription factors, in a PI-l-dependent fashion. Structurally, (I-IX),, repeats in Corrc.~potrt/~ttrc adhm: C. Sander, Europcdn Molecular Biology Laboratory, Mcycrholj;trasse I. D-G900 Hcidclbcrg. Germany. Fax: (49) (6221) 38 7306.
an extended conformation can present linear arrays of His side chains, which can associate in pairs by coordinating metal ions like Zn” or Cu” (Fig. 2). This structure could be termed a ‘histidine-metal zipper’. Consistent with this structural model is the observation in known three-dimensional structures that Pro often occurs adjacent to His in metal binding sites of enzymes 1131.
Interacting (HX),, repeats could guide the formation of dimers or of networks of transcription factors. An example may be the 74E gene products and E75A, which have been shown to bind to early and late puffs on Drosophih polytene chromosomes, after induction of third larval instar salivary glands with 20-hydroxyecdysone (for a review see [14]). It is tempting to speculate that this coordinated binding involves interaction via the (HX),, repeats. An intriguing property of protein-protein interactions mediated by (HX),, would be sensitivity to pH. As the p.& of a hicrid;nP side chain is in the range of phy...-_.- _.___.__ siological pH values, a small shift in intracellular p!-l could have a dramatic effect on the binding capacity of (HX),, repeats. By this mechanism extracellular inductors like growth factors, which can increase lhc intracellular pH by 0.1-0.3 units [IS], might influcncc the association state of an entire network of transcription factors. At the present stage of limited experimental evidence we cannot exclude the possibility of other functional roles of (HX),, repeats: for example, direct binding to DNA or RNA through H-bonds from His side chains to phosphate groups; or, interaction with the acidic do-
December
FEBSLETTERS
Volume295, number1,2,3
199
74E:
658
QwqHPHSql
ngpHPHSH?H
SHPHSHPHAg
qtXHStiaaa
697
Paired:
544
gHAHSHHgHP
HApHPHAHPH
PqyzlgaHPHY
pppsssaHFm
583
Bicoid:
10
fyHHplpHTH
THPHPHSHPH
PHSHPHPHHq
49
Deformed:
73
mtgHPHSmHP
admvsdymaH
HHNpHSHSHS
HPqlqlppqf HTHSlpHHHS
112
113
nsaisgHHqa
saggysrnya
natppsHPHS
HPHAHPHQsl
152
Odd-Skipped:
237
qqqHPHHHHh
HGHPhHPHPH
PHHvrpypag
176
Daughterless:
219
naaiyqqqqq HHslnHTpHA
HSHTlplpHA
1pHGiiTlpHP H;isqqnspav
258
Cfla:
298
HHggyHPHHd
mHGspmgtX
HSHSppmlsp
qnmqssavaa
237
";75A:
156
HHHPqqeHQp
hHPHPHVmyp
HGyqqanlHH
195
Chox-1.4:
26
HSgsagssas
qwqgqHHlq yHPhHPHPHA
EiLHAaHPgpa
65
TCR:
48
sHTHRHSyl1
HPHTHVct3T
PPPPPPPPPP HTctHTHIHA
stHVciHTHT
87
ALS-SuRA:
33
fpfpIiHpHKt
tpppIHLtHT
HIHIHSqrrr
ftisnvistn
72
Lrpl:
31
HPHSHApplp
rtptps!iPHS
rasplprapt
ptHPHSHApp
70
Lrp2:
13
HPHSHApplp
rtptpaHPHS
HApplprtpt
ptHPHSHApp
52
Fig.
I. Partial sequences of proteins, primarily
mmscription factors, containing significant (HX),: repeats. The sequences are not slrictly aligncc HX sequences are in capital lelrcrs. Prolcin codes are explained in Uie text.
mains of other transcription factors, which are thou@ to pass stimulatory signals to the transcription machil: ery by interacting with TFIID orTFIIB [16]. We hope that our hypothesis of pH-dependent prc tein-protein interaction between transcription factor mediated by (HX),, repeats will stimulate specific exper. ments. REFERENCES Frigerio. 111
Fig. 2. Approximale molecular model of Iwo PHPHP units imcracting via a bound metal ion. Only IWO HX units arranged ir. antiparallcl are shown here. Longer. zipper-like rcpcaring structures can be generated without violation of stcrcochemislry by simple lalcral displaccmcm in thedirection ofthepolypeptidc backbone. The association of two (HX),, repeats is likely to bc pH.dcpendcnt in the relatively narrow range of inlracellular pH values available to physiological control.
2
G., Burri. M., Bopp, D., Baumgartner. S. and Nell. h (1986) Cell 47, 735-746. v1Janknecht, R., Taube, W., Liidecke, H.-J. and Pangs, 0. (I981 Nucleic Acids Rcs. 17, 4455-4464. 131 Ucrleth, T., Burri. M.. Thoma, G., Bopp, D., Richslcin, S., Prig rio, G., Nell, M. and NUs!ein-Volhard, C. (1988) EMBO J. 1749-1756. R&ski. M., >lcGinnis, N., Chadwick, R. and *McGinnis. V (1987) EMBO J. 6, 767-777. Coulter, D.E.. Swaykus, E.A., Bcran-Kochn, MA., Goldb:: ..__.. D., Wieschaus, E. and Schedi. P. (IWU) EMBO J, 8, 3795-330 Cronmiller, C., Schedl, P. and Clint, T.W. (1988) Genes Dev. lG66-1676. Johnson, W.A. andHirsh, J. (1990) Nature 343,467-470. Segraves, W.A. and Hogncss, D.S. (1990)Gcnes Dcv. 4,204-21 Sasaki, H.. Yokoyama, E. and Kuroiwa. A. (1990)Nucleic Acil Res. 18, 1739-1747. [!O] Angiolillo, A.L., Lamoyi, E., Bernstein, K.E. and Mage, R.( 119851 Proc. Nail. Acad. Sci. USA 82.4498-450!. [I I] iec, K.Y., Townsend, J., Tcpperman,.J., Black, U.. Chui, C.F Mazur, B., Dunsmuir. P. nnd Bedbrook, J. (1985) EMBO J. 1241-1248. [I21 Wcchsler, S-L., Ncsburn, A.B., Zwaagstra, J. nnd Ghiasi, I (1989) Virology 168, 168-172. [l3] Chakrabani, P, (1990) Prot. Engineering 4. 57-63, [I41 Thummcl, C.S. (1990) BioEssays 12, 561-568. [IS] Moolenaar, W.H. (1986) Ann. Rev. Physiol. 48, 363-376. [lb] Sharp, P.A. (1991) Nalurc 351, 16-18.
