I think the answer to your question lies in following questions:
1. Are you using EJBs in your application ?
2. Or any other framework like Spring/Hibernate etc.
Generally I have not seen DAO calling another DAO. DAO to me are specialized extensions of the business components (EJB or POJO), which contain data access code. I think it should be Business component calling another business component.
The transaction handling will come from the first two questions.