Hi !
I propose to you you 2 options :
A/Preserve transparency
1-Create you text layer and animate it.
2-Place at the top your texture’s jpeg and click the case in the T column to preserve transparency.
B/TrkMat
1-Create you text layer and animate it.
2-Place at the bottom of your text layer your texture’s jpeg and do Alpha Matte in the TrkMat Column.
I hope it answers to your question
Denis
Denis Fouché
http://www.redliger.com