Recruitment of the Androgen Receptor via Serum Response Factor Facilitates Expression of a Myogenic Gene

Androgen receptor (AR) induced precocious myogenesis in culture and myogenic specified gene activity. Increased levels of AR expression in replicating C2C12 myoblasts stimulated fusion into post-differentiated multinucleated myotubes and the appearance of skeletal α-actin transcripts, even in the absence of ligand. Furthermore, AR activated the skeletal α-actin promoter, which lacks GRE sites, in co-transfected C2C12 cells. AR co-activation of the skeletal α-actin promoter required co-expressed full-length serum response factor (SRF). In vitro, AR associated with SRF and was recruited by SRF to a α-actin promoter SRF binding site. Our data suggest that AR is capable of activating myogenic genes devoid of consensus AR binding sites via its recruitment by the myogenic enriched transcription factor, SRF. Androgen receptor (AR) induced precocious myogenesis in culture and myogenic specified gene activity. Increased levels of AR expression in replicating C2C12 myoblasts stimulated fusion into post-differentiated multinucleated myotubes and the appearance of skeletal α-actin transcripts, even in the absence of ligand. Furthermore, AR activated the skeletal α-actin promoter, which lacks GRE sites, in co-transfected C2C12 cells. AR co-activation of the skeletal α-actin promoter required co-expressed full-length serum response factor (SRF). In vitro, AR associated with SRF and was recruited by SRF to a α-actin promoter SRF binding site. Our data suggest that AR is capable of activating myogenic genes devoid of consensus AR binding sites via its recruitment by the myogenic enriched transcription factor, SRF. Steroid androgens play an important role in determining lean body mass and muscle strength. For example, men made hypogonadal lose lean body mass and muscle strength (1Mauras N. Hayes V. Welch S. Rini A. Helgeson K. Dokler M. Veldhuis J.D. Urban R.J. J. in in levels with In of hypogonadal men men with androgens muscle strength and lean body mass S. N. J. J. M. J. A. K. Urban R.J. J. by and M. K. J. muscle mass and strength. strength in a M. S. and was to a factor in muscle strength K. A. M. J. muscle K. A. A. M. J. a muscle mass and strength S. J. is that androgens muscle mass and and to the role of androgens skeletal muscle R.J. J. A. J. M. Urban R.J. J. J. of myogenic by androgens is M. S. J. receptor (AR) serum response serum response binding binding skeletal serum response serum response binding binding skeletal is a of the of transcription and the and receptor AR androgens by a the of the J. and binding M. J. and a with the to the receptor in the and AR and transcription S. in in to the and response and V. J. J. AR that myogenic specified genes M. of the receptor is by Steroid to with in of receptor activity. AR to with a of transcription N. N. S. J. M. M. S. S. A. factor A. J. S. A. J. and the of transcription J. J. of a of myogenic genes is binding sites serum response factor (SRF). SRF a of the SRF a that to its sites in a of to and a the binding of that the of gene V. M. R.J. R.J. J. M. S. R.J. M. J. S. SRF is a of gene which in and of myogenic and muscle of and serum response that SRF in a S. J. J. R.J. play in SRF binding muscle gene transcription of gene that the associated with SRF and activity. AR a role in and an SRF AR activated the skeletal α-actin promoter, which lacks GRE sites, in co-transfected C2C12 and the AR was to with SRF and recruited to SRF binding AR was capable of activating a myogenic gene devoid of consensus AR binding sites via its recruitment by SRF. 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C2C12 myoblasts a of culture in co-transfected with of and of in a myoblasts to with and in the of and by in and by C2C12 myoblasts with with in an and an with to was by the to the the and C2C12 myoblasts a of with and to and and by an and an of AR in and by of the to to the an and by in binding by with of SRF. with in and by via to SRF was by by of In of was with the C2C12 myoblasts with in and and the C2C12 was with the AR of serum to of in in in and by and R.J. of SRF binding sites and to to and of the Androgen in C2C12 a of the of binding binding and binding to of and J. the and of C2C12 myoblasts myotubes and to an with myoblasts with the In in to to multinucleated α-actin is a of muscle R.J. K. in the and and fusion in myogenic In C2C12 induced the appearance of a to a appearance of and fusion in C2C12 of that of myogenic R.J. J. in of precocious of a of myoblasts with in to myoblasts a role AR in myogenesis and that is an AR gene a and of the C2C12 of SRF with SRF expression is induced by the of myoblasts in by AR in an that consensus sites AR the promoter to in R.J. J. the to a of of the to with AR SRF to the In C2C12 in R.J. expression of SRF AR activity. of the and SRF by with with and SRF expression with the promoter gene co-activation of AR with SRF in C2C12 myoblasts by promoter by of to SRF and AR myoblasts stimulated promoter transcription to the of AR and SRF stimulated a promoter and was C2C12 myoblasts with the gene the of the promoter and the expression to and of SRF and AR to the skeletal was with of in AR required full-length SRF to skeletal promoter activity. SRF capable of promoter to with with the gene the of the skeletal promoter, and the expression to and activity. 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J. the and of AR with SRF In vitro, AR capable of SRF recruitment of the and of the and the of In and the Our data that of a the of and was of was to SRF In that is AR SRF. that the AR and activated promoter, AR full-length to with SRF the skeletal promoter, in with the AR data that the AR binding with SRF. In vitro, with SRF was by recruitment of SRF the and by recruitment of by the SRF the and the to with and that the strength of the of SRF with full-length SRF was AR to skeletal promoter in cells. the was of of a by with SRF and SRF of the of in AR skeletal promoter that SRF AR of the SRF SRF with AR with the that AR and SRF and that AR and SRF to of in of the AR is in the AR and the SRF in the AR and of the of transcription factor J. K. J. SRF the of V. M. of the of to was required to V. J. is the and receptor V. S. to AR and SRF is a and receptor via binding SRF and AR of the that a of of AR SRF the skeletal promoter of to SRF AR an by expression of a AR skeletal of of skeletal promoter levels with which the in was by a to of with that the that a of and AR the myogenic gene by the of the SRF gene skeletal was by AR and ligand. SRF is a transcription factor to the myogenic and skeletal α-actin AR the to a of Steroid androgens play an important role in determining lean body mass and muscle strength. For example, men made hypogonadal lose lean body mass and muscle strength (1Mauras N. Hayes V. Welch S. Rini A. Helgeson K. Dokler M. Veldhuis J.D. Urban R.J. J. in in levels with In of hypogonadal men men with androgens muscle strength and lean body mass S. N. J. J. M. J. A. K. Urban R.J. J. by and M. K. J. muscle mass and strength. strength in a M. S. and was to a factor in muscle strength K. A. M. J. muscle K. A. A. M. J. a muscle mass and strength S. J. is that androgens muscle mass and and to the role of androgens skeletal muscle R.J. J. A. J. M. Urban R.J. J. J. of myogenic by androgens is M. S. J. receptor (AR) serum response serum response binding binding skeletal serum response serum response binding binding skeletal is a of the of transcription and the and receptor AR androgens by a the of the J. and binding M. J. and a with the to the receptor in the and AR and transcription S. in in to the and response and V. J. J. AR that myogenic specified genes M. of the receptor is by Steroid to with in of receptor activity. AR to with a of transcription N. N. S. J. M. M. S. S. A. factor A. J. S. A. J. and the of transcription J. J. of a of myogenic genes is binding sites serum response factor (SRF). SRF a of the SRF a that to its sites in a of to and a the binding of that the of gene V. M. R.J. R.J. J. M. S. R.J. M. J. S. SRF is a of gene which in and of myogenic and muscle of and serum response that SRF in a S. J. J. R.J. play in SRF binding muscle gene transcription of gene that the associated with SRF and activity. AR a role in and an SRF AR activated the skeletal α-actin promoter, which lacks GRE sites, in co-transfected C2C12 and the AR was to with SRF and recruited to SRF binding AR was capable of activating a myogenic gene devoid of consensus AR binding sites via its recruitment by SRF. AR induced precocious muscle in culture and a of myogenic gene activity. myoblasts in a in with and in a in with J. was via to into M. expression and into by of and receptor J. was the was with and and to that with the of the and the to and to with and binding was with and and into that was with to which AR SRF in the R.J. and a of with J. was a with the to of the skeletal α-actin promoter of the gene is R.J. J. of myoblasts a of in which was to with of the of culture the in and by a the of the skeletal α-actin gene S. was with and and with of the to and in a of and with of to the in and R.J. J. For receptor in the M. which a to AR in C2C12 myoblasts For C2C12 with the devoid of a of which the of in and the cells. C2C12 myoblasts a of culture in co-transfected with of and of in a myoblasts to with and in the of and by in and by C2C12 myoblasts with with in an and an with to was by the to the the and C2C12 myoblasts a of with and to and and by an and an of AR in and by of the to to the an and by in binding by with of SRF. with in and by via to SRF was by by of In of was with the C2C12 myoblasts with in and and the C2C12 was with the AR of serum to of in in in and by and R.J. of SRF binding sites and to to and myoblasts in a in with and in a in with J. was via to into M. expression and into by of and receptor J. was the was with and and to that with the of the and the to and to with and binding was with and and into that was with to which AR SRF in the R.J. and a of with J. was a with the to of the skeletal α-actin promoter of the gene is R.J. J. of myoblasts a of in which was to with of the of culture the in and by a the of the skeletal α-actin gene S. was with and and with of the to and in a of and with of to the in and R.J. J. For receptor in the M. which a to AR in C2C12 myoblasts For C2C12 with the devoid of a of which the of in and the cells. C2C12 myoblasts a of culture in co-transfected with of and of in a myoblasts to with and in the of and by in and by C2C12 myoblasts with with in an and an with to was by the to the the and For C2C12 myoblasts a of with and to and and by an and an of AR in and by of the to to the an and by in binding by with of SRF. with in and by via to SRF was by by of In of was with the C2C12 myoblasts with in and and the C2C12 was with the AR of serum to of in in in and by and R.J. of SRF binding sites and to to and of the Androgen in C2C12 a of the of binding binding and binding to of and J. the and of C2C12 myoblasts myotubes and to an with myoblasts with the In in to to multinucleated α-actin is a of muscle R.J. K. in the and and fusion in myogenic In C2C12 induced the appearance of a to a appearance of and fusion in C2C12 of that of myogenic R.J. J. in of precocious of a of myoblasts with in to myoblasts a role AR in myogenesis and that is an AR gene a and of the C2C12 of SRF with SRF expression is induced by the of myoblasts in by AR in an that consensus sites AR the promoter to in R.J. J. the to a of of the to with AR SRF to the In C2C12 in R.J. expression of SRF AR activity. of the and SRF by with with and SRF expression with the promoter gene co-activation of AR with SRF in C2C12 myoblasts by promoter by of to SRF and AR myoblasts stimulated promoter transcription to the of is a of a binding and to a the R.J. made SRF to the of SRF that required co-activation with devoid of SRF R.J. AR M. J. co-activation of promoter was in co-transfected full-length SRF was to with AR in of the of SRF in the of AR of and SRF of the of Androgen by SRF SRF AR in the SRF binding a of the skeletal promoter, to J.D. J. R.J. was and was and by that AR is recruited by in the of SRF the of a of with SRF. 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J. in of precocious of a of myoblasts with in to myoblasts a role AR in myogenesis and that is an AR gene a and of the C2C12 of SRF with SRF expression is induced by the of myoblasts in by AR in an that consensus sites AR the promoter to in R.J. J. the to a of of the to with AR SRF to the In C2C12 in R.J. expression of SRF AR activity. of the and SRF by with with and SRF expression with the promoter gene co-activation of AR with SRF in C2C12 myoblasts by promoter by of to SRF and AR myoblasts stimulated promoter transcription to the of SRF is a of a binding and to a the R.J. made SRF to the of SRF that required co-activation with devoid of SRF R.J. AR M. J. co-activation of promoter was in co-transfected full-length SRF was to with AR in of the of SRF in the of AR of and SRF of the of Androgen by SRF SRF AR in the SRF binding a of the skeletal promoter, to J.D. J. R.J. was and was and by that AR is recruited by in the of SRF the of a of with SRF. 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Our suggest that of the AR with SRF. the AR was recruited by to a by SRF data that SRF and AR SRF and recruitment of AR binding that the SRF the of the recruited AR SRF to by which the skeletal muscle required the and that of muscle in of and and the fusion of with In the the role of AR in muscle was K. S. J. skeletal muscle that C2C12 with AR skeletal and and that AR C2C12 and stimulated levels to in the absence of promoter was stimulated by AR and SRF binding In myoblasts gene to gene was to levels by of AR by with SRF via to a of AR to in the absence of in and levels of that AR in the and AR with SRF. expression of AR in AR to J. J. the and of AR with SRF In vitro, AR capable of SRF recruitment of the and of the and the of In and the Our data that of a the of and was of was to SRF In that is AR SRF. that the AR and activated promoter, AR full-length to with SRF the skeletal promoter, in with the AR data that the AR binding with SRF. In vitro, with SRF was by recruitment of SRF the and by recruitment of by the SRF the and the to with and that the strength of the of SRF with full-length SRF was AR to skeletal promoter in cells. the was of of a by with SRF and SRF of the of in AR skeletal promoter that SRF AR of the SRF SRF with AR with the that AR and SRF and that AR and SRF to of in of the AR is in the AR and the SRF in the AR and of the of transcription factor J. K. J. SRF the of V. M. of the of to was required to V. J. is the and receptor V. S. to AR and SRF is a and receptor via binding SRF and AR of the that a of of AR SRF the skeletal promoter of to SRF AR an by expression of a AR skeletal of of skeletal promoter levels with which the in was by a to of with that the that a of and AR the myogenic gene by the of the SRF gene skeletal was by AR and ligand. SRF is a transcription factor to the myogenic and skeletal α-actin AR the to a of by which the skeletal muscle required the and that of muscle in of and and the fusion of with In the the role of AR in muscle was K. S. J. skeletal muscle that C2C12 with AR skeletal and and that AR C2C12 and stimulated levels to in the absence of promoter was stimulated by AR and SRF binding In myoblasts gene to gene was to levels by of AR by with SRF via to a of AR to in the absence of in and levels of that AR in the and AR with SRF. expression of AR in AR to J. J. the and of AR with SRF In vitro, AR capable of SRF recruitment of the and of the and the of In and the Our data that of a the of and was of was to SRF In that is AR SRF. that the AR and activated promoter, AR full-length to with SRF the skeletal promoter, in with the AR data that the AR binding with SRF. In vitro, with SRF was by recruitment of SRF the and by recruitment of by the SRF the and the to with and that the strength of the of SRF with In full-length SRF was AR to skeletal promoter in cells. the was of of a by with SRF and SRF of the of in AR skeletal promoter that SRF AR of the SRF SRF with AR with the that AR and SRF and that AR and SRF to of in of the AR is in the AR and the SRF in the AR and of the of transcription factor J. K. J. SRF the of V. M. of the of to was required to V. J. is the and receptor V. S. to AR and SRF is a and receptor via binding SRF and AR of the that a of of AR SRF the skeletal promoter of to SRF AR an by expression of a AR skeletal of of skeletal promoter levels with which the in was by a to of with that the that a of and AR the myogenic gene by the of the SRF gene skeletal was by AR and ligand. SRF is a transcription factor to the myogenic and skeletal α-actin AR the to a of of the of