Complex sentence: The Cyclin D/Cdk4 complex is a compound structure of Cyclin D and Cdk4, regulated by the GATA-1 transcription factor.
Split into simpler sentences: The Cyclin D/Cdk4 complex is a multi-protein structure consisting of the proteins Cyclin D and cyclin-dependent kinase 4, or Cdk4. It is regulated by the GATA-1 transcription factor.