Shelbourne moved 11 points clear at the top of the First Division after a 1-0 win at bottom side Wexford.
Georgie Poynton got the winner for the unbeaten Dubliners from the penalty spot in the 32nd minute.
UCD were hammered 4-0 at Bray - their third defeat on the bounce - but retain second place over Treaty United and Galway United on goal difference.
Darren Craven and Conor Clifford netted before the break for Bray and sub Joe Doyle scored twice in the second half to complete the rout.
The result takes the Seagulls to within a point of fifth-placed Cabinteely, who lost 1-0 in Galway.
Galway spurned a number of chances but still made it back-to-back wins thanks to Wilson Waweru's first-half strike.
Cork City closed the gap between them and seventh-placed Athlone to four points after a 2-0 win in the Midlands.
Alec Byrne and Jack Baxter scored just before half-time and full-time respectively as the Rebels secured their first away win in 22 months.
Cobh Ramblers host Treaty United on Saturday.