The invention relates to methods of making modular chimeric protein expressionproducts and compositions utilized in the methods. In particular, the inventionrelates to sequential, directional cloning of polynucleotides encoding polypeptidemodules. Each clonable element or module contains an open reading frame of interestflanked by predetermined restriction sites. The methods include using modulesand vectors containing these modules as starting materials for recombinantDNA techniques. One advantage of the invention is that it allows for many variationsof fusion proteins to be made quickly and easily without needing to design andevaluate each subsequent cloning step.
