PVST+ and STP can work together without any further configuration. Cisco has built this PVST+ over simple PVST to solve this issue. even if you connect 2 region of PVST+ through STP network, 2 regions can send each other complete information of PVST+ by building some level of tunneling with setting the destination MAC address to special multicast MAC (0100.0ccc.cccd). with this configuration, the CST region of network (that uses just STP) will not see receiving messages as BPDU and forward them as normal multicast. I hope u get your answer.