1.Cook pasta in large saucepan of boiling water, uncovered, until tender; drain. Rinse pasta under cold water; drain.
2.Meanwhile, boil, steam or microwave beans until just tender; drain. Rinse under cold water; drain.
3.Drain tuna over small bowl; reserve oil for dressing. Flake tuna in large chunks with fork.
4.To make lemon dressing, place ingredients with reserved oil in screw-top jar; shake well.
5.Place pasta, beans and tuna in large bowl with dressing and remaining ingredients; toss gently to combine.