if this is your MOBO: https://www.asus.com/Motherboards/M5A78L-M-PLUS-USB3/specifications/
GTX 1050 requires PCIe 3.0 which still can run on PCIe 2.0 but no one can guarantee it's compatibility and performance (it should be fine i had experience running same setup with different card and mobo).
i will go with GTX 970 if you wanna play on high/ultra settings some modern games.
if this is your MOBO: https://www.asus.com/Motherboards/M5A78L-M-PLUS-USB3/specifications/
GTX 1050 requires PCIe 3.0 which still can run on PCIe 2.0 but no one can guarantee it's compatibility and performance (it should be fine i had experience running same setup with different card and mobo).
i will go with GTX 970 if you wanna play on high/ultra settings some modern games.