title: Annotation Track in Gviz
body: <p>Does anyone with experience using the <code>bioconductor</code> package: <code>Gviz</code> know how to add an <code>AnnotationTrack</code> directly over a <code>DataTrack</code>? </p>
  
  <p>For example, in <code>ggplot2</code> I can add to a prexitsting plot using + <code>geom_text</code>, but I haven't been able to locate a similar feature for <code>Gviz</code> </p>
  
  <p>Thanks!</p>