List the cast member of the movies whose producer is Mark Johnson.
SELECT DISTINCT ?uri WHERE { ?x <http://dbpedia.org/ontology/producer> <http://dbpedia.org/resource/Mark_Johnson_(producer)> . ?x <http://dbpedia.org/ontology/starring> ?uri  . ?x <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://dbpedia.org/ontology/Film>}
Mark_Johnson_(producer)