HOUSTON — Case Keenum threw for a career-high 559 yards and had five touchdowns, his last coming with 21 seconds remaining, and No. 15 Houston escaped with a 50-43 win over Southern Mississippi on Saturday.

Keenum broke the tie with a 28-yard pass to Patrick Edwards. The Golden Eagles had a chance to tie it, but Martevious Young's heave from midfield was knocked down in the end zone as the final seconds ticked off the clock.

Keenum's other TD passes went for 33, 55, 14 and 17 yards as Houston won its fourth straight game. James Cleveland finished with 13 catches for 190 yards, and Charles Sims ran 95 yards as the two teams combined 1,358 yards and 66 first downs.

The Cougars (7-1, 3-1 Conference USA) led by seven and were driving to put the game away when Korey Williams forced a fumble by Bryce Beall, which Southern Miss recovered on its own 23.

The Golden Eagles (5-4, 3-2) marched downfield and tied it 43-all on a 13-yard reception by Gerald Baptiste with 57 seconds left.

Southern Miss had cut the lead to 43-36 on a 5-yard touchdown reception by Baptiste with 5½ minutes left. That score was helped by a 36-yard quarterback draw by Young moments earlier.

Baptiste finished with 186 yards receiving and three scores, while Young was 20 of 34 for 334 yards and ran for another 70.

Keenum had already thrown for more yards than the season-low 233 yards he had last week with 11½ minutes left before halftime. He had 244 yards passing after a 55-yard catch and run score by Tim Monroe that made it 21-13.

Southern Miss answered with a 1-yard run by Young, but Daniel Hrapmann's extra point attempt was blocked and Nick Saenz returned it to push Houston's lead to 23-19. After a field goal by Southern Miss, Keenum threw his third TD of the half to make it 30-22 at the break.

Matt Hogan added a 34-yard field goal early in the third quarter, and Keenum's second touchdown pass to Cleveland made it 40-22 early in the fourth.

The back-and-forth game continued when Southern Miss finished off a 70-yard drive with Tory Harrison's 1-yard run with about 9 minutes remaining. Hogan then answered with a 23-yard field goal that extended the lead to 43-29.

Southern Miss was in the game the entire way, mostly it took advantage of mistakes. The Golden Eagles scored nine points off two first-half turnovers, including Williams' fumble recovery on the first play of the game that set up Fletcher's 6-yard TD run.

The extra point was blocked, but an interception in the end zone by Eddie Hicks led to a 29-yard field goal by Hrapmann that got Southern Miss within 23-22 about 3 minutes before halftime.

Hrapmann missed a 32-yarder in the third quarter.